Chapter C: E. Dutton, Critical observations on theories of the earth’s (4)

Mineralogy to-day would certainly be generally considered one of the minor members of the group of the Geological Sciences. We commonly look upon it in the light of an useful handmaiden, whose chief function is to serve the other branches, and we are inclined to forget that, in reality, mineralogy was the first to be recognized and, with considerable truth, might be claimed as the mother of all the others. Minerals, because of their frequent beauty of color and form, and their uses as gems and as ornamental stones, were the first inorganic objects to excite wonder and comment and we find many of them named and described in very early writings. Theophrastus (368–284 B. C.), a famous pupil of Aristotle, wrote a treatise “On Stones” in which he collected a large amount of information about minerals and fossils. The elder Pliny (23–79 A. D.), more than three centuries later, in his Natural History, described and named many of the commoner minerals. At this time it was natural that no clear distinction should be drawn between minerals and rocks, or even between minerals and fossils. As long as all study of the materials of the earth’s crust was concerned with their superficial characters, it was logical to include everything under the single head. There were some writers in the early centuries of the Christian era, however, who believed that fossils had been derived from living animals but the majority considered them to be only strange and unusual forms of minerals. During many succeeding centuries little was added to the general store of geological knowledge and it was not until the beginning of the sixteenth century, that any further notable progress was made. Agricola (1494–1555) was a physician, who, for a time, lived in the mining district of Joachimstal. He studied and described the minerals that he collected there. He was the first to give careful and critical descriptions of minerals, of their crystals and general physical properties. Unfortunately, he also did not realize the fundamental distinction between fossils and minerals, and probably because of his influence this error persisted, even until the middle of the eighteenth century. But, naturally, as the number of scientific students increased, the number of those who rejected this conclusion grew, until at last, the true character of fossils was established. The keen interest in minerals and fossils which was aroused by this controversy, together with the rapid extension of mining operations, drew the attention of scientific men to other features of the earth’s surface and led to a more extended investigation of its characters and thus to the development of geology proper. It is interesting to note also that mineralogy was the first of the Geological Sciences to be officially recognized and taught by the universities.

Although, as has been shown, the beginnings of mineralogy lie in the remote past, the science, as we know it to-day, can be said to have had practically its whole growth during the last one hundred years. Of the more than one thousand mineral species that may now be considered as definitely established hardly more than two hundred were known in the year 1800 and these were only partially described or understood. It is true that Haüy, the “father of crystallography,” had before this date discovered and formulated the laws of crystal symmetry, and had shown that rational relations existed between the intercepts upon the axes of the different faces of a crystal. It was not until 1809, however, that Wollaston described the first form of a reflecting goniometer, and thus made possible the beginning of exact investigation of crystals. The distinctions between the different crystal groups were developed by Bernhardi, Weiss and Mohs between the years 1807 and 1820, while the Naumann system of crystal symbols was not proposed until 1826. The fact that doubly refracting minerals also polarize light was discovered by Malus in 1808, and in 1813 Brewster first recognized the optical differences between uniaxial and biaxial minerals. The modern science of chemistry was also just beginning to develop at this period, enabling mineralogists to make analyses more and more accurately and thus by chemical means to establish the true character of minerals, and to properly classify them.

Franz von Kobell, on page 372 of his “Geschichte der Mineralogie,” somewhat poetically describes the condition of the science at this period as follows: “With the end of the eighteenth and the commencement of the nineteenth centuries exact investigations in mineralogy first began. The mineralogist was no longer content with approximate descriptions of minerals, but strove rather to separate the essential facts from those that were accidental, to discover definite laws, and to learn the relations between the physical and chemical characters of a mineral. The use of mathematics gave a new aspect to crystallography, and the development of the optical relationships opened a magnificent field of wonderful phenomena which can be described as a garden gay with flowers of light, charming in themselves and interesting in their relations to the forces which guide and govern the regular structure of matter.”

In the Medical Repository (vol. =2=, p. 114, New York, 1799), there occurs the following notice: “Since the publication of the last number of the Repository an Association has been formed in the city of New York ‘for the investigation of the Mineral and Fossil bodies which compose the fabric of the Globe; and, more especially, for the Natural and Chemical History of the Minerals and Fossils of the United States,’ by the name and style of The American Mineralogical Society.” With this announcement is given an advertisement in which the society “earnestly solicits the citizens of the United States to communicate to them, on all mineralogical subjects, but especially on the following: 1, concerning stones suitable for gun flints; 2, concerning native brimstone or sulphur; 3, concerning salt-petre; 4, concerning mines and ores of lead.” Further the society asks “that specimens of all kinds be sent to it for examination and determination.”

This marks apparently the beginning of the serious study of the science of mineralogy in the United States. From this time on, articles on mineralogical topics appeared with increasing frequency in the Medical Repository. Most of these were brief and were largely concerned with the description of the general characters and modes of occurrence of various minerals. Nothing of much moment from the scientific point of view appeared until many years later, but the growing interest in things mineralogical was clearly manifest. An important stimulus to this increasing knowledge and discussion was furnished by Col. George Gibbs who, about the year 1808, brought to this country a large and notable mineral collection. In the Medical Repository (vol. 11, p. 213, 1808), is found a notice of this collection, a portion of which is reproduced below:

“Gibbs’ grand Collection of Minerals.

One of the most zealous cultivators of mineralogy in the United States
is Col. G. Gibbs of Rhode Island and his taste and his fortune have
concurred in making him the proprietor of the most extensive and
valuable assortment of minerals that probably exists in America.

This rich collection consists of the cabinets possessed by the late
Mons. Gigot D’Orcy of Paris and the Count Gregoire de Rozamonsky, a
Russian nobleman, long resident in Switzerland. To which the present
proprietor has added a number, either gathered by himself on the spot,
or purchased in different parts of Europe.... The whole consists of
about twenty thousand specimens. A small part of this collection was
opened to amateurs at Rhode Island, the last summer, and the next, if
circumstances permit, the remainder will be exposed.”

In 1802 Benjamin Silliman was appointed professor of chemistry and mineralogy in Yale College. After the Gibbs Collection was brought to America he spent much time with the owner in studying it and, as a result, Col. Gibbs offered to place the collection on exhibition in New Haven if suitable quarters would be furnished by the college. This was quickly accomplished and in 1810, 1811 and 1812 the collection was transferred to New Haven and arranged for exhibition by Col. Gibbs. Later, in 1825, it was purchased by Yale and served as the nucleus about which the present Museum collection of the University has been formed. There is no doubt but that the presence at this early date of this large and unusual mineral collection had a great influence upon the development of mineralogical science at Yale, and in the country at large.

In the year 1810 Dr. Archibald Bruce started the “American Mineralogical Journal,” the title page of which reads in part as follows: “The American Mineralogical Journal, being a Collection of Facts and Observations tending to elucidate the Mineralogy and Geology of the United States of America, together with other Information relating to Mineralogy, Geology and Chemistry, derived from Scientific Sources.” Unfortunately the health of Dr. Bruce failed, and the journal lasted only through its first volume. It had, however, “been most favorably received,” as Silliman remarks, and it was felt that another journal of a similar type should be instituted. Such a suggestion was made by Col. Gibbs to Professor Silliman in 1817 and this led directly to the founding of the American Journal of Science in 1818 under the latter’s editorship. Although the field of the Journal at the very beginning was made broad and inclusive it has always published many articles on mineralogical subjects. Three of its editors-in-chief have been eminent mineralogists, and without question it has been the most important single force in the development of this science in the country. More than 800 well-established mineral species have been described since the year 1800, of which approximately 150 have been from American sources. More than two-thirds of the articles describing these new American minerals have first appeared in the pages of the Journal. While the description of new species is not always the most important part of mineralogical investigation, still these figures serve to show the large part that the Journal has played in the growth of American mineralogy.

It is convenient to review the progress in Mineralogy according to the divisions formed by the different series, consisting of fifty volumes each, in which the Journal has been published. These divisions curiously enough will be found to correspond closely to four quite definite phases through which mineralogical investigation in America has passed. The first series covered the years from 1817 to 1845. In looking through these volumes one finds a large number of mineralogical articles, the work of many contributors. The great majority of these papers are purely descriptive in character, frequently giving only general accounts of the mineral occurrences of particular regions. However, a number of articles dealing with more detailed physical and chemical descriptions of rare or new species also belong in this period. Among the mineralogists engaged at this time in the description of individual species, none was more indefatigable than Charles U. Shepard. He was graduated from Amherst College in 1824, at the age of twenty. In 1827 he became assistant to Professor Silliman in New Haven, continuing in this position for four years. Later he was a lecturer in natural history at Yale, and was at various times connected with Amherst College and the South Carolina Medical College at Charleston. His articles on mineralogy were very numerous. He assigned a large number of new names to minerals, although with the exception of some half dozen cases, these have later been shown to be varieties of minerals already known and described, rather than new species. In spite, however, of his frequent hasty and inaccurate decision as to the character of a mineral, his influence on the progress of mineralogy was marked. His great enthusiasm and ceaseless industry throughout a long life could not help but make a definite contribution to the science. His “Treatise on Mineralogy” will be spoken of in a later paragraph. He died in May, 1886, having published his last paper in the Journal in the previous September.

The first book on mineralogy published in America was that by Parker Cleaveland, professor of mathematics, natural philosophy, chemistry and mineralogy in Bowdoin College. The first edition was printed in 1816 and an exhaustive notice is given in the first volume of the Journal (1, 35, 308, 1818); a second edition followed in 1822. In his preface Cleaveland gives an interesting discussion concerning the two opposing European methods of classifying minerals. The German school, led by Werner, classified minerals according to their external characters while the French school, following Haüy, put the emphasis on the “true composition.” Cleaveland remarks that “the German school seems to be most distinguished by a technical and minutely descriptive language; and the French, by the use of accurate and scientific principles in the classification or arrangement of minerals.” He, himself, tried to combine in a measure the two methods, basing the fundamental divisions upon the chemical composition and using the accurate description of the physical properties to distinguish similar species and varieties from each other.

Cleaveland’s mineralogy was followed nearly twenty years later by the Treatise on Mineralogy by Charles U. Shepard already mentioned. The first part of this book was published in 1832. This contained chiefly an account of the natural history classification of minerals according to the general plan adopted by Mohs, the Austrian mineralogist. The second part of the book, which appeared in 1835, gave the description of individual species, the arrangement here being an alphabetical one throughout. Subsequent editions appeared in 1844, 1852 and 1857.

James Dwight Dana was graduated from Yale College in 1833 at the age of twenty. Four years later (1837) he published “The System of Mineralogy,” a volume of 580 pages. The appearance of this book was an event of surpassing importance in the development of the science. The book, of course, depended largely upon the previous works of Haüy, Mohs, Naumann and other European mineralogists, but was in no sense merely a compilation from them. Dana, particularly in his discussion of mathematical crystallography, showed much original thought. He also proved his originality by proposing and using an elaborate system of classification patterned after those already in use in the sciences of botany and zoology. He later became convinced of the undesirability of this method of classification and abandoned it entirely in the fourth edition of the System, published in 1854, substituting for it the chemical classification which, in its essential features, is in general use to-day. The System of Mineralogy started in this way in 1837, has continued by means of successive editions to be the standard reference book in the subject. The various editions appeared as follows: I, 1837; II, 1844; III, 1850; IV, 1854; V, 1868; VI, 1892 (by Edward S. Dana).

J. D. Dana also contributed numerous mineralogical articles to the first series of volumes of the Journal. It is interesting to note that they are chiefly concerned with the more theoretical aspects of the subject, in fact they constitute practically the only articles of such a character that appeared during this period. Among the subjects treated were crystallographic symbols, formation of twin crystals; pseudomorphism, origin of minerals in metamorphosed limestones, origin of serpentine, classification of minerals, etc.

The volumes of the Second Series of the Journal covered the years from 1846 through 1870. This period was characterized by great activity in the study of the chemical composition of minerals. A number of skilled chemists, notably J. Lawrence Smith, George J. Brush and Frederick A. Genth, began about 1850 a long series of chemical investigations of American minerals. Very few articles during this time paid much attention to the physical properties of the minerals under discussion, practically no description of optical characters was attempted, and only occasionally were the crystals of a mineral mentioned. J. D. Dana was almost the only writer who constantly endeavored to discover the fundamental characters and relationships in minerals. He published many articles in these years which were concerned chiefly with the classification and grouping of minerals, with similarities in the crystal forms of different species, with relations between chemical composition and crystal form, chemical formulas, mineral nomenclature, etc. The following titles give an idea of the character of the more important series of articles by him which belong to this category: On the isomorphism and atomic volume of some minerals (=9=, 220, 1850); various notes and articles on homœomorphism of minerals (=17=, 85, 86, 210, 430; =18=, 35, 131, 1854); on a connection between crystalline form and chemical constitution, with some inferences therefrom (=44=, 89, 252, 398, 1867).

A great many new mineral names were proposed between 1850 and 1870, a large number of which have continued to be well-recognized species. But there was also a tendency, which has not wholly disappeared even now, to base a mineral determination upon insufficient evidence, and to propose a new species with but little justification for it. In this connection a quotation from the introduction by J. D. Dana to the 3rd Supplement to the System of Mineralogy (4th edition) published in the Journal (=22=, page 246, 1856), will be of interest. He says:

“It is a matter of regret, that mineral species are so often brought
out, especially in this country, without sufficient investigation and
full description. It is not meeting the just demands of the science of
mineralogy to say that a mineral has probably certain constituents, or
to state the composition in a general way without a complete and
detailed analysis, especially when there are no crystallographic
characters to afford the species a good foundation. We have a right to
demand that those who name species, should use all the means the
science of the age admits of, to prove that the species is one that
nature will own, for only such belong to science, and if enough of the
material has not been found for a good description there is not enough
to authorize the introduction of a new name in the science. The
publication of factitious species, in whatever department of science,
is progress not towards truth, but into regions of error; and often
much and long labor is required before the science recovers from these
backward steps.”

J. Lawrence Smith was born in 1818 and died in 1883. He was a graduate of the University of Virginia and of the Medical College of Charleston and later spent three years studying in Paris. Shortly after the completion of his studies he went to Turkey as an advisor to the government of that country in connection with the growing of cotton there. During this time he investigated the emery mines of Asia Minor, and wrote a memoir upon them which was later published by the French Academy. He served as professor of chemistry in the University of Virginia and later held the same chair in the University of Illinois. He published a long series of papers on the chemical composition of minerals and meteorites, as well as on pure chemical subjects. Among the more notable of his contributions are the “Memoir on Emery” (1850), a series of papers on the “Reëxamination of American Minerals” (1853) written with the collaboration of George J. Brush, and his “Memoir on Meteorites” (1855).

George J. Brush entered on his scientific career at the moment when science and scientific methods of research were just beginning to be appreciated in this country, and he soon became one of the leading pioneers in the movement. While his half century of active service was largely occupied by administrative duties in connection with the Sheffield Scientific School, his interest in mineralogy never flagged. His papers on mineralogical subjects number about thirty, all of which were published in the Journal. These began in 1849, even before his graduation from college, and continued until his last paper (in collaboration with S. L. Penfield) appeared in 1883. Three of the early papers were written with J. Lawrence Smith as noted above. These papers first set in this country the standard for thorough and accurate scientific mineral investigation. Later in life he was active in the development of the remarkable mineral locality at Branchville, Conn., and, with the collaboration of E. S. Dana, published in the Journal (1878–90) five important articles on its minerals. This locality, with the exception of the zinc deposits at Franklin Furnace, N. J., was the most remarkable yet discovered in this country. Nearly forty different mineral species were found there, of which nine (mostly phosphates) were new to science. There has certainly been no other series of descriptive papers on a mineralogical locality of equal importance published in this country.

In addition to publishing original papers, Brush did considerable editorial work in connection with the fourth (1854) and fifth (1868) editions of the System of Mineralogy and the Appendices to them. His Manual of Determinative Mineralogy, with a series of determinative tables adapted from similar ones by von Kobell, was first published in 1874. It was revised in 1878 and later rewritten by S. L. Penfield. This book did much to make possible the rapid and accurate determination of mineral species. Throughout his life, Brush was an enthusiastic collector of minerals, building up the notable collection that now bears his name. Perhaps, however, his most important contribution to the development of mineralogy in America lay rather in his influence upon his many students. With his enthusiasm for accurate and painstaking investigation he was an inspiration to all who came in contact with him and his own field and science in general owes much to that influence.

Among the early mineralogists in this country, who were concerned in the chemical analyses of minerals, none accomplished more or better work than Frederick A. Genth. He was born in Germany in 1820 and lived in that country until 1848, when he came to the United States and settled in Philadelphia. He had studied in various German universities and worked under some of the most famous chemists of that time. His papers in mineralogy number more than seventy-five, in the great majority of which chemical analyses are given. He published fifty-four successive articles, the greater part of which appeared in the Journal, which were entitled Contributions to Mineralogy. In these he gave descriptions of more than two hundred different minerals, most of which were accompanied by analyses. He described more than a dozen new and well-established mineral species. He was especially interested in the rarer elements and many of his analyses were of minerals containing them. Especially interesting was his work with the tellurides, the species coloradoite, melonite and calaverite being first described by him. A long and important investigation was recorded on Corundum, “Its Alterations and Associate Minerals,” published in the Proceedings of the American Philosophical Society in 1873 (=13=, 361). Dr. Genth died in 1893.

The period from 1860 until 1875 was not very productive in mineralogical investigations. The first ten volumes of the Third Series of the Journal, covering the years 1871–1876, contained mineralogical articles by only some fifteen different authors. But from that time on, the amount of work done and the number of investigators grew rapidly. With this increase in activity came also a decided change in the character of the work. The period between 1871 and 1895 can be characterized as one in which all the various aspects of mineral investigation received more nearly equal prominence. While the chemical composition of minerals still held rightly its prominent place, the investigation of the crystallographic and optical characters and the relationships existing between all three were of much more frequent occurrence. Edward S. Dana commenced his scientific work by publishing in 1872 an article on the crystals of datolite which was probably the first American article concerned wholly with the description of the crystallography of a mineral. Samuel L. Penfield began his important investigations in 1877 and the first articles by Frank W. Clarke appeared during this period. The first edition of the Text Book of Mineralogy by Edward S. Dana with its important chapters on Crystallography and Optical Mineralogy was published in 1877 and his revision of the System of Mineralogy (sixth edition) appeared in 1892.

Unquestionably the foremost figure in American mineralogy during this period was that of Samuel L. Penfield. He embodied in an unusual degree the characters making for success in this science, for few investigators in mineralogy have shown, as he did, equal facility in all branches of descriptive mineralogy. He was a skilled chemist and possessed in a high degree that ingenuity in manipulation so necessary to a great analyst. He was also an accurate and resourceful crystallographer and optical mineralogist. His contributions to the science of mineralogy can be partially judged by the following brief summary of his work. He published over eighty mineralogical papers, practically all of which were printed in the Journal. These included the descriptions of fourteen new mineral species, the establishment of the chemical composition of more than twenty others, and the crystallization of about a dozen more. By a series of brilliant investigations he established the isomorphism between fluorine and the hydroxyl radical. He first enunciated the theory that the crystalline form of a mineral was due to the mass effect of the acid present rather than that of the bases. He contributed also a number of articles on the stereographic projection and its use in crystallographic investigations, devising a series of protractors and scales to make possible the rapid and accurate use of this projection in solving problems in crystallography.

Penfield was born in 1856, was graduated from the Sheffield Scientific School in 1877 and immediately became an assistant in the chemical laboratory of that institution. At this time he, together with his colleague Horace L. Wells, made the analyses of the minerals from the newly discovered Branchville locality. He spent the years 1880 and 1881 in studying chemistry in Germany, returning to Yale as an instructor in mineralogy in the fall of 1881. Except for another semester in Europe at Heidelberg he continued as instructor and professor of mineralogy in the Sheffield Scientific School until his early death in 1906.

It is difficult to choose for mention the names of other investigators in Mineralogy during this period. Toward its end a great many writers contributed to the pages of the Journal, more than fifty different names being counted for the volumes =41= to =50= of the Third Series. Many of these are still living and still active in scientific research. Mention should be made of Frank W. Clarke, who contributed many important articles concerning the chemical constitution of the silicates. His work on the mica and zeolite groups is especially noteworthy. The work of W. H. Hillebrand, particularly in regard to his analytical investigations of the minerals containing the rarer elements, was of great importance. The name of W. E. Hidden should be remembered, because, with his keen and discriminating eye and active search for new mineral localities, he was able to make many additions to the science.

In glancing over the indices to the Journal the close interrelation of mineralogy to the other sciences is strikingly shown by the fact that so many scientists whose particular fields are along other lines have published occasional mineralogical papers. Frequently a young man has commenced with mineralogical investigations and then later been drawn definitely into one of these allied subjects. Men, who have won their reputation in chemistry, physics, and all the various divisions of geology, even that of palaeontology, have all contributed articles distinctly mineralogical in character. For this reason the number of American writers who have published what may be called casual papers on mineralogy is very great in comparison to the number of those who continue such publications over a series of years.

That the subject of meteorites is one which has been constantly studied by American mineralogists and petrographers is shown by the long list of papers concerning it that have been published in the Journal; it should, therefore, be considered briefly here. Many of these papers are short and of a general descriptive nature but others which give more fully the chemical, mineralogical and physical details are numerous. Among the earlier writers on this subject Benjamin Silliman, Jr., and C. U. Shepard should be mentioned. The latter was the first to recognize a new mineral in the Bishopville meteorite which he called chladnite. The same substance was afterwards found in a terrestial occurrence and was more accurately described by Kenngott under the name of enstatite. J. Lawrence Smith later showed that these two substances were identical. Smith did a large amount of important chemical work on meteorites. He was the first to note the presence of ferrous chloride in meteoric iron, the mineral being afterwards named lawrencite in his honor. The iron-chronium sulphide, daubreelite, was also first described by him. Other names that should be mentioned in this connection are those of A. W. Wright who studied the gaseous constituents of meteorites, G. F. Kunz, W. E. Hidden, A. E. Foote and H. A. Ward, all of whom published numerous descriptions of these bodies. Among the more recent workers in this field the names of G. P. Merrill and O. C. Farrington deserve especial mention.

The publication of the Fourth Series of the Journal began in 1896. Although the years since then have seen a great amount of very important work accomplished, the history of the period is fresh in the minds of all and as the majority of the active workers are still living and productive it seems hardly necessary to go into great detail concerning it. Twenty years ago it seemed to some mineralogists that the science could almost be considered complete. All the commoner minerals had certainly been discovered and exhaustively studied. Little apparently was left that could be added to our knowledge of them. New occurrences would still be recorded, new crystal habits would be observed, and an occasional new and small crystal face might be listed, but few facts of great importance seemed undiscovered. This view was not wholly justified because new facts of interest and importance have continuously been brought forward, and the finding of new minerals does not appear to diminish in amount with the years. The work of the investigators on the United States Geological Survey along these lines is especially noteworthy.

This last of our periods, however, is chiefly signalized by a practically new development along the lines that might be characterized as experimental mineralogy. New ways have been discovered in which to study minerals. The important but hitherto baffling problems of their genesis, together with their relations to their surroundings, and to associated minerals, have been attacked by novel methods.

In this pioneer work that of the Geophysical Laboratory of the Carnegie Institution of Washington has been of the greatest importance. This laboratory was established in 1905 and, under the directorship of Arthur L. Day, a notable corps of investigators has been assembled and remarkable work already accomplished. While the field of investigation of the laboratory is broader than that of mineralogy, including much that belongs to petrography, vulcanology, etc., still the greater part of the work done can be properly classed as mineralogical in character and should be considered here. Because of its great value, however, it was felt that an authoritative, although necessarily, under existing conditions, a brief, account of it should be given. A concise summary of the objects, methods and results of the investigations of the laboratory has been kindly prepared by a member of its staff, Dr. R. B. Sosman, and is given later.

During the last few years another line of investigation has been opened by the discovery of the effect of crystalline structure upon X-rays. Through the refraction or reflection of the X-ray by means of the ordered arrangement of the particles forming the crystalline network, we are apparently going to be able to discover much concerning the internal structure of crystals. And, partly through these discoveries, is likely to come in turn the solution of the hitherto insolvable mystery of the constitution of matter. Without doubt the multitudinous facts of mineralogy assembled during the past century by the painstaking investigation of a large number of scientists are destined to play a large part in the solution of this problem. Further, it does not seem too bold a prophecy to suggest, that the time will come when it will be possible to assemble all these unorganized facts that we know about minerals into a harmonious whole and that we shall be then able to formulate the underlying and fundamental principles upon which they all depend. These are the great problems for the future of mineralogical investigation.

IX
THE WORK OF THE GEOPHYSICAL LABORATORY OF THE CARNEGIE INSTITUTION OF
WASHINGTON

By R. B. SOSMAN

There are three methods of approach to the great problem of rock formation. The first undertakes to reproduce by suitable laboratory experiments some of the observed changes in natural rocks. The second seeks to apply the principles of physical chemistry to a great body of carefully gathered statistics. The third method of attack is like the first in being a laboratory method, and like the second in seeking to apply existing knowledge to the association of minerals as found in rocks, but in its procedure differs widely from both. It consists of bringing together pure materials under measurable conditions, and thus in establishing by strictly quantitative methods the relations in which minerals can exist together under the conditions of temperature and pressure that have the power to affect such relations.

It is to this third method of investigation of the problems of the rocks that the Geophysical Laboratory has been devoted since its establishment in 1905. It has proved entirely practicable to make quantitative studies of the relations among the principal earth-forming oxides (silica, alumina, magnesia, lime, soda, potash, and the oxides of iron) over a very wide range of temperatures. The resources of physics have proved adequate to establish temperature with a high degree of precision and to measure the quantity of energy involved in the various reactions. The chemist has been able to obtain materials in a high degree of purity, and to follow out in detail the chemical relationships that exist among the earth-forming oxides. The petrographic laboratory has been available for the comparison of synthetic laboratory products with the corresponding natural minerals.

It has also proved entirely practicable to extend the same methods of research to some of the principal ore minerals such as the sulphides of copper. Other information which is certain to be of ultimate economic value has also come out of the thorough study of the silicates, which are basic materials for the vast variety of industries which are classed under the name of ceramic industries. The best example of this is the facility with which the experience and the personnel of the laboratory has been adapted to the very important problem of manufacturing an adequate supply of optical glass for the needs of the United States in the present war.

It has further been possible to show within the last two years that rock formation in which volatile ingredients play a necessary and determining part can be completely studied in the laboratory with as much precision as though all the components were solids or liquids.

Along with the laboratory work on the formation of minerals and rocks has gone an increasing amount of field work on the activities of accessible volcanoes, such as Kilauea and Vesuvius, where the fusion and recrystallization of rocks on a large scale can be observed and studied.

There was once a time when the confidence of the laboratory in the capacity of physics and chemistry to solve geological problems was not shared by all geologists. There were some who were inclined to view with considerable apprehension the vast ramifications and complications of natural rock formation as a problem impossible of adequate solution in the laboratory. It is, therefore, a matter of satisfaction to all those who have participated in these efforts to see the evidences of this apprehension disappearing gradually as the work has progressed. A careful appraisement of the situation to-day, after ten years of activity, reveals the fact that the tangible grounds for anxiety about the _accessibility_ of the problems which were confronted at first are now for the most part dissipated.

It will not be possible to review in detail the lines of work sketched above. An outline of the synthetic work on systems of the mineral oxides and a paragraph on the volcano researches will perhaps suffice to indicate the general plan and purpose of the laboratory’s work. It should be added that the results of many of the researches of the laboratory, detailed below, have been published in the pages of the Journal (see =21=, 89, 1906, and later volumes).

_Mineral Researches._—The mineral studies include:

I. _One-component systems_: silica, with its numerous polymorphic forms and their relations to temperature and the conditions of rock formation; alumina; magnesia; and lime.

II. _Two-component systems_: silica-alumina, including sillimanite and related minerals; silica-magnesia, including the tetramorphic metasilicate MgSiO_{3}; silica-lime, including wollastonite; the alkali silicates, particularly with reference to their equilibria with carbon dioxide and with water; ferric oxide-lime; alumina-lime; alumina-magnesia, including spinel; and hematite-magnetite, a solid-solution series of an unusual type.

III. _Three-component systems_: silica-alumina-magnesia, completed but not yet published; silica-alumina-lime, complete, including the compounds that enter into the composition of portland cement; silica-magnesia-lime, completed but not yet published, including, however, published work on the diopside-forsterite-silica system, and on the CaSiO_{3}-MgSiO_{3} series; and alumina-magnesia-lime.

IV. _Four components_: SiO_{2}-Al_{2}O_{3}-MgO-CaO: the incomplete system anorthite-forsterite-silica; SiO_{2}-Al_{2}O_{3}-CaO-Na_{2}O: the series of lime-soda feldspars (albite-anorthite), and the series nephelite (carnegieite)-anorthite; SiO_{2}-Al_{2}O_{3}-Na_{2}O-K_{2}O: the sodium-potassium nephelites.

V. _Five components_: SiO_{2}-Al_{2}O_{3}-MgO-CaO-Na_{2}O: the ternary system diopside-anorthite-albite (haplo-basaltic and haplo-dioritic magmas).

Fairly complete studies have also been made of the mineral sulphides of iron, copper, zinc, cadmium, and mercury, and the conditions controlling the secondary enrichment of copper sulphide ores are now being investigated. In connection with the sulphide investigations, the hydrated oxides of iron have been studied chemically and microscopically and the results will soon be ready for publication.

Throughout the work the mere accumulation of bodies of facts has been held to be secondary in importance to the development of new methods of attack and the evaluation of new general principles, and the specific problems studied have been selected from this point of view.

_Volcano Researches._—A branch of the laboratory’s work that is of general as well as petrological interest is the study of active volcanoes. Observations and collections have been made at Kilauea, Vesuvius, Etna, Stromboli, Vulcano, and (through the courtesy of the directors of the National Geographic Society) Katmai in Alaska. The great importance of gases in volcanicity is emphasized by all the studies. The active gases include hydrogen and water vapor, carbon monoxide and carbon dioxide, and sulphur and its oxides, as well as a variety of other compounds of lesser importance. The crater of Kilauea proves to be an active natural gas-furnace, in which reactions are continuously occurring among the gases, often resulting in making the lava basin hotter at the surface than it is at some depth. These reactions are being studied in the laboratory on mixtures of the pure constituent gases in known proportions, in order to lay the foundation for accurate interpretation and prediction concerning the gases as actually collected from the volcanoes themselves.

X
THE PROGRESS OF CHEMISTRY DURING THE PAST ONE HUNDRED YEARS

By HORACE L. WELLS and HARRY W. FOOTE

_Introduction._

As we look back to the time of the founding of the Journal in 1818, we see that the science of chemistry had recently made and was then making great advances. That the scientific men of those days were much impressed with what was being accomplished is well shown by the following statement made in an early number of the Journal (=3=, 330, 1821) by its founder in reviewing Gorham’s Elements of Chemical Science. He says: “The present period is distinguished by wonderful mental activity; it might indeed be denominated as the intellectual age of the world. At no former period has the mind of man been directed at one time to so many and so useful researches.”

A very remarkable revolution in chemical ideas had recently taken place. Soon after the discovery of oxygen by Priestley in 1774, and the subsequent discovery by Cavendish that water was formed by the combustion of hydrogen and oxygen, Lavoisier had explained combustion in general as oxidation, thus overthrowing the curious old phlogiston theory which had prevailed as the basis of chemical philosophy for nearly a century.

The era of modern chemistry had thus begun, and the additional views that matter was indestructible and that chemical compounds were of constant composition had been generally accepted at the beginning of the nineteenth century.

Dalton had announced his atomic theory in 1802, having based it largely upon the law of multiple proportions which he had previously discovered, and he had begun to express the formulas for compounds in terms of atomic symbols.

In 1808 Gay-Lussac had discovered his law of gas combination in simple proportions,[153] a law of supreme importance in connection with the atomic theory, but neither he nor Dalton had seen this theoretical connection. Avogadro had understood it, however, and in 1811 had reached the momentous conclusion that all gases and vapors have equal numbers of molecules in equal volumes at the same temperature and pressure.

Davy in 1807 had isolated the alkali-metals, sodium and potassium, by means of electrolysis, thus practically dispelling the view that certain earthy substances might be elementary; and about four years later he had demonstrated that chlorine was an element, not an oxide as had been supposed previously, thus overthrowing Lavoisier’s view that oxygen was the characteristic constituent of all acids.

At the time that our period of history begins, the atomic theory had been accepted generally, but in a somewhat indefinite form, since little attention had been paid to Avogadro’s principle, and since Dalton had used only the principle of greatest simplicity in writing the formulas of compounds, considering water as HO and ammonia NH, for example. At this time, however, Berzelius for ten or fifteen years had been devoting tremendous energy to the task of determining the atomic weights of nearly all of the elements then known by analyzing their compounds. He had confirmed the law of multiple proportions, accepted the atomic theory, and utilized Avogadro’s principle, and it is an interesting coincidence that his first table of atomic weights was published in the year 1818.

An interesting account of the views on chemistry held at about that time was published in the Journal by Denison Olmsted (=11=, 349, 1826; =12=, 1, 1827), who had recently become professor of natural philosophy in Yale College.

The most illustrious European chemists of that time were Berzelius of Sweden, Davy of England, and Gay-Lussac of France, and the curious circumstance may be mentioned that all three of them and also Benjamin Silliman, the founder of the Journal, were born within a period of eight months in 1778–1779.

In this country Robert Hare of Philadelphia and Benjamin Silliman were undoubtedly the most prominent chemists of those days. Hare is best known for his invention of the compound blowpipe, but his contributions to the Journal were very numerous, beginning almost with the first volume and continuing for over thirty years. Among the first of these contributions was a most vigorous but well-merited attack upon a Doctor Clark of Cambridge, England, who had copied his invention without giving him proper credit. He begins (=2=, 281, 1820) by saying: “Dr. Clark has published a book on the gas blowpipe in which he professes a sincere desire to render everyone his due. That it would be difficult for the conduct of any author to be more discordant with these professions, I pledge myself to prove in the following pages.”

Hare also invented a galvanic battery which he called a “deflagrator,” consisting of a large number of single cells in series. With this, using carbon electrodes, he was able to obtain a higher temperature than with his oxy-hydrogen blowpipe. He was the first to apply galvanic ignition to blasting (=21=, 139, 1832), and he first carried out electrolyses with the use of mercury as the cathode (=37=, 267, 1839). In this way he prepared metallic calcium and other metals from solutions of their chlorides, while the principle employed by him has in recent times been used as the basis of a very important process for manufacturing caustic potash and soda.

Silliman, who had become an intimate friend of Hare during two periods of chemical study under Woodhouse in Philadelphia in 1802–1804, and who soon afterwards spent fourteen months as a student abroad, chiefly in England and Scotland, took a broad interest in science and gave much attention to geology as well as to chemistry. In spite of this divided interest and his work as a teacher, popular scientific lecturer, and editor, he found time for a surprising amount of original chemical work. For instance, using Hare’s deflagrator, he showed that carbon was volatilized in the electric arc (=5=, 108, 1822); he was the first in this country to prepare hydrofluoric acid (=6=, 354, 1823), and he first detected bromine in one of our natural brines (=18=, 142, 1830).

_Atomic Weights._

As soon as the atomic theory was accepted, the relative weights of the atoms became a matter of vital importance in connection with formulas and chemical calculations. In advancing his theory, Dalton had made some very rough atomic weight determinations, and it has been mentioned already that Berzelius, at the time that our historical period begins, was engaged in the prodigious task of accurately determining these constants for nearly all the known elements. It is recorded that he analyzed quantitatively no less than two thousand compounds in connection with this work during his career. His table of 1818 has proved to be remarkably accurate for that pioneer period, and it indicates his remarkable skill as an analyst.

It is to be observed that Berzelius in this early table made use of Avogadro’s principle in connection with elements forming gaseous compounds, and thus obtained correct formulas and atomic weights in such cases, but that in many instances his atomic weights and those now accepted bear the relation of simple multiples to one another, because he had then no means of deciding upon the formulas of many compounds except the rule of assumed simplicity. For example, the two oxides of iron now considered to be FeO and Fe_{2}O_{3} he regarded as FeO_{2} and FeO_{3}, knowing as he did that the ratio of oxygen in them was 2 to 3, and believing that a single atom of iron in each was the simplest view of the case, so that as the consequence of these formulas the atomic weight of iron was then considered to be practically twice as great in its relation to oxygen as at present.

These old atomic weights of Berzelius, used with the corresponding formulas, were just as serviceable for calculating compositions and analytical factors as though the correct multiples had been selected. As time went on, the true multiples were gradually found from considerations of atomic heats, isomorphism, vapor densities, the periodic law, and so on, and suitable changes were made in the chemical formulas.

Berzelius used 100 parts of oxygen as the basis of his atomic weights, a practice which was generally followed for several decades. Dalton, however, had originally used hydrogen as unity as the basis, and this plan finally came into use everywhere, as it seemed to be more logical and convenient, because hydrogen has the smallest atomic weight, and also because the atomic weights of a number of common elements appeared to be exact multiples of that of hydrogen, thus giving simpler numbers for use in calculations.

Within a few years a slight change has been made by the adoption of oxygen as exactly 16 as the basis, which gives hydrogen the value of 1·008.

As early as 1815, Prout, an English physician, had advanced the view that hydrogen is the primordial substance of all the elements, and consequently that the atomic weights are all exact multiples of that of hydrogen. This hypothesis has been one of the incentives to investigations upon atomic weights, for it has been found that these constants in the cases of a considerable number of the elements are very close to whole numbers when based upon hydrogen as unity, or even still closer when based upon oxygen as 16.

With our present knowledge Prout’s hypothesis may be regarded as disproved for nearly all the elements whose atomic weights have been accurately determined, but the close or even exact agreement with it in a few cases is still worthy of consideration. There is an interesting letter from Berzelius to B. Silliman, Jr., in the Journal (=48=, 369, 1845) in which Berzelius considers the theory entirely disproved.

For a long time entire reliance was placed upon the atomic weights obtained by Berzelius, but it came to be observed that the calculation of carbon from carbon dioxide appeared to give high results in certain cases, so that doubt arose as to the accuracy of Berzelius’s work. Consequently in 1840 Dumas, assisted by his pupil Stas, made a new determination of the atomic weight of carbon, and found that the number obtained by Berzelius, 12·12, was slightly too large. Subsequently Dumas determined more than twenty other atomic weights, but this great amount of work did not bring about any considerable improvement, for it appears that Dumas did not greatly excel Berzelius in accuracy, and that the latter had made one of his most noticeable errors in connection with carbon.

Soon after assisting Dumas in the work upon carbon, Stas began his very extensive and accurate, independent determinations, leading to the publication of a book in 1867 describing his work. Stas made many improvements in methods by the use of great care in purifying the substances employed, and especially by using large quantities of material in his determinations, thus diminishing the proportional errors in weighing. His results, which dealt with most of the common elements, were accepted with much confidence by chemists everywhere.

Stas reached the conclusion that there could be no real foundation for Prout’s hypothesis, since so many of his atomic weights varied from whole numbers, and this opinion has been generally accepted.

The first accurate atomic weight determination published in the Journal was that by Mallett on lithium (=22=, 349, 1856; =28=, 349, 1859), showing a result almost identical with that accepted at the present time. Johnson and Allen’s determination (=35=, 94, 1863) on the rare element cæsium was carried out with extraordinary accuracy. Lee, working with Wolcott Gibbs, made good determinations on nickel and cobalt (=2=, 44, 1871). The work of Cooke on antimony (=15=, 41, 107, 1878) was excellent.

Concerning the more recent work published elsewhere than in the Journal, attention should be called particularly to the investigations that have been carried on for the past twenty-five years by Richards and his associates at Harvard University. Richards has shown masterly ability in the selection of methods and in avoiding errors. His results have displayed such marvelous agreements among repeated determinations by the same and by different processes as to inspire the greatest confidence. His work has been very extensive, and it is a great credit to our country that this atomic weight work, so superior to all that has been previously done, is being carried out here.

It may be mentioned that for a number of years the decision in regard to the atomic weights to be accepted has been in the hands of an International Committee of which our fellow countryman F. W. Clarke has been chairman. In connection with this position and previously, Clarke has done valuable service in re-calculating and summarizing atomic weight determinations.

_Analytical Chemistry._

Analysis is of such fundamental importance in nearly every other branch of chemical investigation that its development has been of the utmost importance in connection with the advancement of the science. It attained, therefore, a comparatively early development, and one hundred years ago it was in a flourishing condition, particularly as far as inorganic qualitative and gravimetric analysis were concerned. There is no doubt that Berzelius, whose atomic weight determinations have already been mentioned, surpassed all other analysts of that time in the amount, variety, and accuracy of his gravimetric work. He lived through three decades of our period, until 1848.

During the past century there has been constant progress in inorganic analysis, due to improved methods, better apparatus and accumulated experience. An excellent work on this subject was published by H. Rose, a pupil of Berzelius, and the methods of the latter, with many improvements and additions by the author and others, were thus made accessible. Fresenius, who was born in 1818, did much service in establishing a laboratory in which the teaching of analytical chemistry was made a specialty, in writing text-books on the subject and in establishing in 1862 the “Zeitschrift für analytische Chemie,” which has continued up to the present time.

Besides Berzelius, who was the first to show that minerals were definite chemical compounds, there have been many prominent mineral analysts in Europe, among whom Rammelsberg and Bunsen may be mentioned, but there came a time towards the end of the nineteenth century when the attention of chemists, particularly in Germany, was so much absorbed by organic chemistry that mineral analysis came near becoming a lost art there. It was during that period that an English mineralogist, visiting New Haven and praising the mineral analyses that were being carried out at Yale, expressed regret that there appeared to be no one in England, or in Germany either, who could analyze minerals.