Chapter VII: ASTRONOMY, ETC--On Determining the Sun's Distance by a (3)

The apparatus, as a whole, has for base a cast-iron reservoir; A, to the top of which is fixed the pump properly so-called, B, as well as the clack box, A, and safety valve. The pump is placed opposite an upright, D, whose top serves as a guide to the prolongation, E, of the piston rod. This latter is traversed by a pivot, a (Fig 19), on which is mounted a lever, F, whose outer extremity is articulated with a connecting rod, G, which is itself connected with the cranked shaft, G¹. This shaft has for its bearings two supports, b, attached to the reservoir, and carries the driving pulleys and a fly wheel. The beam, F, having to give motion to the piston in describing an arc of a circle at the extremity attached to the connecting rod, must, for that reason, have a fixed point of oscillation, or one that we must consider as such for the instant. Now, such point is selected on a piece, H, having the shape of the letter C, and which plays an important part in the working of the pump. This piece is really a two-armed lever, having its center of oscillation in two brackets, c, at the base of the reservoir. Fig. 17 shows the relation of the beam, F, and lever, H. The upper extremity of this latter is forked, and embraces the beam, F, whose external surfaces are provided with two slots, d, in which to move slides, e, attached to studs, f, which are perfectly stationary on the extremities of the forks of the lever, H. One of the slots is shown in section on the line 1--2 in Fig. 20, and on the line 3--4 in Fig. 21.

Things thus arranged, if we suppose the piece, H, absolutely stationary, it is clear that, as the oscillation of the beam, F, is effected on the studs, f, as centers, the piston of the pump will perform an invariable travel whose extent will be dependent upon its position between such point of oscillation and the point of articulation of the connecting rod, G. But we must observe that even according to such a hypothesis, the point, f, would not be entirely stationary, because the point of articulation, a, upon the piston rod being obliged to follow an invariably straight line, the slots, d, will have to undergo an alternate sliding motion on the slides, e, save, be it understood, when the latter are brought to coincide exactly with the center of articulation, a. Now we shall, in fact, see that the point, f, can move forward in following the slots, d, and that it may even reach the point of articulation, a, of the beam, F, on the rod, E, that is to say, occupy the position shown in Fig. 18, where the oscillation of the beam, F, being effected according to the point, a, the stroke of the piston has become absolutely null.

The position of the piece, H, is, in effect, variable with the pressures that are manifested in the pump. It will be seen that the latter has a tubular appendage, g, in whose interior there plays what is called a "starting rod," h, which is constantly submitted to the pressures existing in the interior of the pump, and which rests against the lower arm, H¹, of the piece, H. But this latter is also loaded at the opposite side with heavy counterpoises, i, which counterbalance, within a determinate limit, the action of the rod, h, that tends constantly to cause the lever, H, to oscillate around its pivot, in the brackets, c.

To sum up, then, as long as the pressure in the pump has not reached a determinate limit, the lever, H, held by its counterpoises, _i_, will keep the position shown in Fig. 16, and for which the center of oscillation, f, corresponds with the maximum stroke of the pump piston. But as soon as such limit is exceeded, the equilibrium being broken, the action of the rod, h, predominates, the piece, H, reverses from right to left, the point of oscillation, f, moves forward in the slots, d, and the stroke of the piston is reduced just so much. If, finally, the pressure continues to increase, the motion of the piece, H, will continue, and the point of oscillation, f, will reach the position for which the motion of the piston ceases completely (Fig. 18).

But it results further, therefrom, that if when such position is reached, the pressure diminishes, the lever, H, will, under the influence of its counterpoise, tend to return to its first position and thus set the piston in motion. As we remarked in the beginning, the automatism of these functions is absolutely complete.

It will be remarked that the piece, H, is provided with an appendage, H², whose interior forms a rack. This rack engages with a pinion, I, mounted on an axle, J, which carries externally a fly wheel, K. This axle, J, moves with the various displacements of the lever, and its fly wheel overcomes by its inertia all backward and forward shocks resulting from the thrusts due to the sliding of the steel slides in the different positions of the connecting rods. Such shocks would make themselves especially felt while the dead centers were being passed.

The velocity with which this pump runs varies from 75 to 80 revolutions per minute. It easily gives a pressure of 200 atmospheres. With a hydraulic press having a piston O.27 of a meter in diameter, it permits of effecting in ten minutes the extraction of the oil from 25 kilogrammes of colza seeds. Referring to the drawings, the scales for Figures 16, 17, 18 are one-fifteenth actual size, and Figures 19, 20, 21, one-tenth.--_Machines, Outils et Appareils_.

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IMPROVED DREDGER.

We illustrate below a dredger of simple construction, well calculated for doing useful work on shallow streams. The barge is 54 ft. long, 22 ft. beam, and 6 ft. deep. Her draught of water is under 4 ft. Built by Rose, Downs & Thompson Hull. Our drawing explains itself. It will be seen that we have here a swiveling crane and grab bucket, and that the stuff dredged can be loaded into the barge and conveyed where necessary. The lifting power of the crane is one ton, and in suitable material such a dredger can get through a great deal of work in a comparatively short time.--_Engineer_.

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HISTORY OF THE FIRE EXTINGUISHER.

The first fire extinguishers were of the "annihilator" pattern, so arranged in a building that when a fire occurred carbonic acid gas was evolved, and, if the conditions were right (as the mediums say), the fire was put out. It worked very nicely at experimental fires built for the purpose, but was apt to fail in case of an involuntary conflagration. About the year 1867 a patent was granted to Carlier and Vignon, of France, for an apparatus in which water saturated with carbonic acid gas was projected upon the fire by the expansive force of the gas itself. As the apparatus was portable and the stream could be directed to any point, it was obviously the desideratum needed. Mr. D. Miles, of Boston, purchased the American patent, and subsequently sold the territory, exclusive of New England, to the Babcock Co., who, at the time, had a crude apparatus of their own. The first machines sold under the new patent were filled with water and loaded with cartridges of dry acid and bicarbonate of soda--the cap screwed down hastily, and, as the chemicals dissolved, the gas was generated, the pressure raised, and the water charged by absorption. The pressure of some 80 pounds was sufficient to project a stream 50 feet or more, and the machine was set upon the shelf so as to be ready for any fire that might occur. In many cases, however, the pressure escaped after a short time, and the machine when needed was found to be useless.

The most important step in the evolution of the modern extinguisher was the adoption of a device for mixing liquid acid with the soda solution, by the turning of a handle or screw, _after_ the alarm was given. This was a practical machine, and proved of such value that an immense business was built up. The result of this prosperity was the development of new companies with new devices for accomplishing the same result, which were successfully offered to the public with varying success.

As these were direct infringements upon the patent rights acquired by the Babcock Company, their encroachments were resisted in the courts, and much money was spent in the effort of the company to sustain their rights, including the purchase of the patents of several rival machines that possessed real merit or whose business was worth controlling. Among these purchases was the right and good will of the "National" Extinguisher Co., who used an acid cartridge of glass, the acid being liberated by breaking the glass. This feature, united with important improvements in general construction and the use of a peculiar glass bottle instead of a tube, is the Babcock machine of to-day, the combination making the simplest and most effective and reliable apparatus ever built. In the meantime, an investigation before the courts brought out the fact that the French patent was antedated by an American invention, for which a patent was applied by a Dr. Graham, in 1837. and which possessed the essential features of the principle in dispute. Graham, through lack of means, or for some other reason, had failed to perfect his papers up to the time of his death, and, as the invention was one of obvious importance, a bill was passed through Congress for the reopening of the case, and the patent was issued to the Graham heirs in 1878. Soon after the issue of the Graham patent, several extinguisher firms, viz, Charles T. Holloway, of Baltimore; W. K. Platt, of Philadelphia; S.F. Hayward of New York; the Protection Fire Annihilator Co., of New York; the Babcock Manufacturing Co., of Chicago, and the New England Fire Extinguisher Co., of Northampton, Mass., were licensed to manufacture under the patent, by Archibald Graham, as administrator of the estate of his father, who bound himself in these licenses to issue no other licenses except with the approval of all those who were included in the combination. This arrangement left several enterprising manufacturers out in the cold, and one of these, in investigating the status of extinguisher patents at Washington, discovered an assignment of a quarter interest of the Graham patent to a Mr. Burton, who, at the time of Graham's second application for a patent, had assisted him with $500. This assignment had long been forgotten--Burton having died, and his heirs knowing nothing of its existence. The widow of Burton was hunted up, an assignment was secured for $30,000, and a consolidated fire extinguisher company was formed, which became the owner of the one quarter interest in the patent. This combination, known as the "Fire Extinguisher Manufacturing Co.," included the Protective Annihilator Co., of New York; the Northampton Fire Extinguisher Co, of Northampton, Mass.; and the North American Fire Annihilator Co., of Philadelphia. The combination bought out the Babcock Co., who had already acquired the patents of the Champion Co., all the patents of the Conellies, of Pittsburg, and of the Great American Co., of Louisville, as well as the licenses of S. F. Hayward and W. K. Platt. This covers all the extinguisher patents in existence, except those of Charles T. Holloway, of Baltimore.

The advantages of the chemical engine are well summed up in the following statement:

The superiority of a chemical engine consists--

1st. In its simplicity. It dispenses with complex machinery, experienced engineers, reservoirs, and steam. Carbonic acid gas is both the working and extinguishing agent.

2d. In promptness. It is always ready. No steam to be raised, no fire to be kindled, no hose to be laid, and no large company to be mustered. The chemicals are kept in place, and the gas generated the instant wanted. In half the cases the time thus saved is a building saved. Five minutes at the right time are worth five hours a little later.

3d. In efficiency. Mere water inadequately applied feeds the fire, but carbonic acid gas never. Bulk for bulk, it is forty times as effective as water, the seventy gallons of the two smallest cylinders being equal to twenty-eight hundred gallons of water. Besides, it uses the only agent that will extinguish burning tar, oil, and other combustible fluids and vapors. One cylinder can be recharged while the other is working, thus keeping up a continuous stream.

4th. In convenience. Five or six men can draw it and manage it. Its small dimensions require but small area, either for work or storage. One hundred feet or more of its light, pliant hose can be carried on a man's arm up any number of stairs inside a building, or, if fire forbids, up a ladder outside.

5th. In saving from destruction by water what the fire has spared. It smothers, but does not deluge; the modicum of water used to give momentum to the gas is soon evaporated by the heat, doing little or no damage to what is below. This feature of the engine is of incalculable worth to housekeepers, merchants, and insurance companies.

6th. Economy. It costs only about half as much as a first class hand engine, and about one-fourth as much as a steam engine, with their necessary appendages, and the chemicals for each charge cost less than two dollars.

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HOW TO TOW A BOAT.

A correspondent of _Engineering News_ says: Those living on swift streams, and using small boats, often have occasion to tow up stream. So do surveyors, hunters campers, tourists, and others. One man can tow a boat against a swift current where five could not row.

Where there are two persons, the usual method is for one to waste his strength holding the boat off shore with a pole, while the other tows. Where but one person, he finds towing almost impossible, and when bottom too muddy for poling and current too swift for rowing, he makes sad progress.

The above cut shows how one man can easily tow alone. The light regulating string, B, passes from the stern of the boat to one hand of the person towing, T. The tow line, A, is attached a little in front of the center of the boat. Hence when B is slackened the boat approaches the shore, while a very slight pull on it turns the boat outward. The person towing glances back "ever and anon" to observe the boat's line of travel.

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RAILWAYS OF EUROPE AND AMERICA.

The following table, which has been prepared by the French Ministry of Public Works, gives the railway mileage of the various countries of Europe and the United States up to the end of last year, with the number of miles constructed in that year, and the population per mile:

Total Built in 1881 Population per Mile

Germany 21,313 331 2,154 Great Britain 18,157 164 1,939 France 17,134 895 2,170 Austria-Hungary 11,880 262 3,200 Italy 5,450 109 5,321 Spain 4,869 176 3,492 Sweden & Norway 4,616 273 1,408 Belgium 2,561 48 2,203 Switzerland 1,557 22 1,831 Holland 1,426 83 2,885 Denmark 1,053 25 1,919 Roumania 916 56 5,860 Turkey 866 - 2,891 Portugal 757 8 5,870 Greece 6 - 28,000 ------- ----- ------ Total 107,306 2,455 3,168 United States 104,813 9,358 502

It appears from this that the United States mileage was only 2,493 less than the total of all Europe, and at the present time it exceeds it, as the former country has built about 6,000 miles this year, whereas Europe has not exceeded 1,500. The difference in the number of persons per mile in the two cases is also very great, Europe taking six times as many persons to support a mile of railway as the States, and can only be accounted for by the fact that American railways are constructed much cheaper than the European ones.

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BEFORE IT HAPPENED.

AT 9 A.M. on Wednesday, September 13, the correspondent of a press agency dispatched a telegram to London with the intimation that the great battle at Tel-el-Kebir was practically over. It may possibly astonish not a few of our readers (says a writer in the _Echo_), to learn that this message reached the metropolis between 7 and 8 o'clock on the same morning; and, in fact, had an unbroken telegraphic wire extended from Kassassin to London, Sir Garnet Wolseley's great victory might have been known here at 6:52 A.M., or (seemingly) at a time when the fight was raging and our success far from complete. Nay, had the telegram been flashed straight to Washington in the United States, it would have reached there something like 1 h. 44 m. after the local midnight of September 12. Paradoxical as this sounds the explanation of it is of the most simple possible character. The rate at which electricity travels has been very variously estimated. Fizeau asserted that its velocity in copper wire was 111,780 miles a second; Walker that it only travels 18,400 miles through that medium during the same interval; while the experiments made in the United States during the determination of the longitudes of various stations there still further reduced the rate of motion to some 16,000 miles a second. Whichever of these values we adopt, however, we may take it for our present purpose, that the transmission of a message by the electric telegraph is practically instantaneous. But be it here noted, there is no such a thing as a _hora mundi_ or common time for the whole world. What is familiarly known as longitude is really the difference in time, east or west, from a line passing through the north and south poles of the earth; and the middle of the great transit circle is the Royal Observatory at Greenwich. If in the latitude of London (51° 30' N.), we proceed 10 miles and 1,383 yards either in an easterly or westerly direction, we find that the local time is respectively either one minute faster or one minute slower than it was at our initial point. Let us try to understand the reason of this. If we fix a tube rigidly at any station on the earth's surface, pointing to that part of the sky in which any bright star is situated when such star is due south (or, as it is technically called, "on the meridian"), and note by a good clock the hour, minute, and second at which it crosses a wire stretched vertically across the tube, then after a lapse of 23 h. 56 m. 4.09 s., will that star be again threaded on the wire. If the earth were stationary--or, rather, if she had no motion but that round her axis--this would be the length of our day. But, as is well known, she is revolving round the sun from left to right; and, as a necessary consequence, the sun seems to be revolving round her from right to left; so that if we suppose the sun and our star to be both on the wire together to-day, to-morrow the sun will appear to have traveled to the left of the star in the sky; and the earth will have that piece more to turn upon her axis before our tube comes up with him again. This apparent motion of the sun in the sky is not an equable one. Sometimes it is faster, sometimes slower; sometimes more slanting, sometimes more horizontal. Thus it comes to pass that solar days, or the intervals elapsing between one return of the sun to the meridian and another, are by no means equal. So a mean of their lengths is taken by adding them up for a year, and dividing by 365; and the quantity to be divided to or subtracted from the instant of "apparent noon" (when the sun dial shows 12 o'clock), is set down in the almanac under the heading of "The Equation of Time." We may, however, here conceive that it is noon everywhere in the northern hemisphere when the sun is due south. Now the earth turns on her axis from west to east, and occupies 24 h. in doing so. As all circles are conceived to be divided into 360°, it is obvious that in one hour 15° must pass beneath the sun or a star; 30° in two hours, and so on. The longitude of Kassassin is, roughly speaking, 32° east, so that when the sun is due south there, or it is noon, the earth must go on turning for two hours and eight minutes before Greenwich comes under the sun, or it is noon there, which is only another way of saying that at noon at Kassassin it is 9 h. 52 m. A.M. at Greenwich. It is this purely local character of time which gives rise to the seeming paradox of our being able to receive news of an event before (by our clocks) it has happened at all.

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THE ADER RELAY.

This new instrument has excited considerable interest among telegraph and telephone men by its exceeding sensitiveness. It is so sensitive to the passage of an electric current that a battery formed with an ordinary pin for one electrode and a piece of zinc wire for the other, immersed in a single drop of water, will give sufficient current to operate the relay. In practice it has successfully worked as a telephonic call on the Eastern Railroad Company's line between Nancy and Paris, a distance of 212 miles, requiring but two cups of ordinary Leclanché battery.

The instrument consists of two permanent horseshoe magnets, fixed parallel with each other and an inch apart. A very thin spool or bobbin of insulated wire is suspended, like the pendulum of a clock, between these permanent magnets, in such a manner that the bobbin hangs just in front of the four poles. A counterpoise is fixed at the top of the pendulum bar, which permits the adjusting of the antagonistic forces represented by the action of the swinging bobbin, and two springs, which are insulated from the mass, and which form one electrode of the local or annunciator circuit, while the pendulum bar forms the other.

It will be easily understood that as the bobbin hangs freely in the center of a very strong magnetic field (formed by the four poles of the two permanent magnets), the slightest current sent through the bobbin will cause the bobbin to be attracted from one direction, while it will be repelled from the other, according to the polarity of the current transmitted.

As the relay has a very low resistance, it is evident that it will become an acceptable auxiliary in our central office, particularly when used as a "calling off" signal, as by its use the ground deviation, so objectionable and yet so universally used for "calling off" purposes, can be entirely avoided, and the relay left directly in the circuit, as is being done here in Paris. R. G. BROWN.

Paris, September 12, 1882.

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THE PLATINUM WATER PYROMETER.

By J. C. HOADLEY.

The following description of the apparatus used for the determination of high temperatures, up nearly to the melting point of platinum, is offered in answer to several inquiries on the subject:

The object to be attained is a convenient and reasonably accurate application of the method of mixtures to the determination of temperatures above the range of mercurial thermometers, say 500° F., up to any point not above the melting point of the most refractory metal available for the purpose, platinum.

A first requisite is a cup or vessel of convenient form, capable of holding a suitable quantity of water, say about two pounds avoirdupois. Berthelot decidedly prefers a simple can of platinum, very thin, with a light cover of the same metal, to be fastened on by a bayonet hitch. For strictly laboratory work this may be the best form; but for the hasty manipulation and rough usage of practical boiler testing something more robust, but, if possible, equally sensitive, is required. The vessel I have used is represented in section in the accompanying cut, Fig. 1.

The inner cell, or true containing vessel, is 4.25 inches in diameter; and of the same height on the side, with a bottom in the form of a spherical segment, of 4.25 inches radius. It is formed of sheet brass 0.01 inch thick, nickel-plated and polished outside and inside. The outer case is 8 inches diameter and 8.5 inches deep, of 16-ounce copper, nickel-plated and polished inside, but plain outside. There are two handles on opposite sides, for convenience of rapid manipulation. The top, of the same copper as the sides and bottom, is depressed conically. like a hopper, and wired at its outer edge, forming a lip all around for pouring out of. The central cell is connected with the outer case only by three rings of hard rubber (vulcanite), each 0.25 inch thick, the middle ring completely insulating the cell from its continuation upward, and from the outer case. A narrow flange is turned outward at the upper edge of the cell, and a similar flange is also turned outward at the lower edge of the cylindrical continuation of the walls of the cell upward. Between these two flanges, the middle ring of hard rubber is interposed, and the two parts, the cell and its upward continuation, are clamped together by the upper and lower rings of hard rubber, which embrace the flanges and are held together by screws. The joints between the flanges and the middle ring of hard rubber, which might otherwise leak a little, are made tight with asphaltum varnish.

Fig 1 shows two partitions, dividing the space between the cell and the case into three compartments, and a concave false bottom. The cover is also seen to be divided into three compartments, by two partitions, and each compartment of the vessel and of its cover is provided with a small tube for inserting a thermometer. This construction was adopted in the first instruments made, for the purpose of observing the rate of heat transmission through the successive compartments, but these parts are without importance with respect to the practical use of the instrument, and may as well be omitted, as they considerably increase the cost, being nickel-plated and polished on both sides. The top and bottom plates of the cover are of 0.01 inch brass, nickel-plated and polished on both sides, both convex outward, the bottom plate but slightly, the top plate to 4.25 inches radius. A ring of hard rubber connects, yet separates and insulates these plates, and they are bound together with the ring into a firm structure by a tube of hard rubber, having a shoulder and knob at the top, and at the lower end a screw-thread engaging with a thin nut soldered to the upper side of the bottom plate. When the cover is in place, its lower plate is even with the top of the cell; and the contained water, which nearly fills the cell, is surrounded by polished, nickel-plated, brass plates 0.01 inch thick, insulated trom other metal by interposed hard rubber. The spaces between the cell and case (a single space if the partitions are omitted), the space above the hard rubber rings, and the space or spaces in the cover are all filled with eider-down, which costs $1.00 per ounce avoirdupois, but a few ounces are sufficient. Soft, fine shavings, or turnings of hard rubber, are said to be excellent as a substitute for eider-down. Heat cannot be confined by any known method. Its transmission can be in some degree retarded, and in a greater degree, perhaps, regulated. Some heat will be promptly absorbed by the sides, bottom, and cover of the cell, and by the agitator; but this does no harm, as its quantity can be accurately ascertained and allowed for. Some will be gradually transmitted to the eider-down, filling the spaces, and through this to the outer casing; but this can be reduced to a minimum by rapid and skillful manipulation, and its quantity, under normal conditions, can be ascertained approximately, so as not to introduce large errors. But varying external influences, such as currents of air, caused by opening doors, or by persons passing along near the apparatus during the progress of an experiment, which would introduce disturbing irregularities, can best be guarded against by such spaces as I have described, filled with the poorest heat-conductor and the lightest _solid_ substance attainable. Air, although a poor heat-conductor, and extremely light, is diathermous, and offers no obstruction to the escape of radiant heat.

The agitator is an important part of the apparatus. Its object, in this instrument, is twofold. _First_, it serves to produce a uniform temperature throughout the body of water in the instrument; and _secondly_, it answers as a support to the heat-carrier of platinum or other metal, often intensely hot, which would injure or destroy the delicate metal of the bottom if allowed to fall on it. For this second purpose, no spiral revolving agitator, such as that commended by Berthelot, would suffice. The best form is such as I have shown in Fig. 1. A concave disk of sheet-brass, made to conform to the shape of the bottom of the cell, with a narrow rim turned up all around, of about 0.02 inch thickness, is liberally perforated with holes to lighten it, and to give free passage to water. The concave form causes the streams of water, produced by slightly raising and lowering the agitator, to take a radial direction downward or upward, so as to cross each other and promote rapid mixing. By a slight modification small vanes might be turned outward from the surface of the metal, which would produce mixing currents if the agitator were given a slight reciprocatory revolving motion, thus avoiding the alternate withdrawal and re-immersion of any part of the stem so strongly deprecated by Berthelot; but for several reasons I think an up and down motion of the agitator desirable in this instrument. The platinum heat carrier, sometimes at a temperature of 2,500° to 2,800° F., is thereby brought into more rapid and forcible contact with the water, steam or water in the spherical condition is washed away from its surface, and by cooling it more rapidly, the duration of the observation is lessened, and errors due to transmission of heat through the walls of the instrument are diminished. The upper part of the agitator stem is of hard rubber, and the brass portion, which terminates at the under side of the cover when the agitator is in its lowest position, suspended by the shoulder at the upper end, need never be lifted for the purpose of mixing out of the hard rubber tube at the cover, so that loss of heat from this cause must be very slight. The brass tube is very freely perforated with holes to admit water, streaming radially through the holes in the agitator, to contact with the thermometer. The hole in the stem at the top is flared, to receive a cork, through which the thermometer is to be passed. The bulb of the thermometer should be elongated, and very slightly smaller in diameter than the stem. After passing it through the cork, a very slight band--a mere thread--of elastic rubber should be put around the bulb, near its lower end, or a thin, narrow shaving of cork may be wound around and tied on, to keep it from contact with the brass tube, for safety; and a little tuft of wool, curled hair, or hard rubber shavings should be put in the bottom of the brass tube to avoid accidents. For the same purpose, a light, but sufficient fender of brass wire, say 0.03 inch diameter, might be judiciously placed around the brass tube at a little distance, to protect it and the thermometer inside of it from shocks from the platinum ball when hastily thrown in, as it must always be. I have had delicate and costly thermometers broken for want of such a fender. Thermometers cannot be too nice for this work. For accurate work at moderate temperatures, they should be about 14 inches long, having a "safe" bulb at the upper end, with a range of 20° F.--32° to 52°--in a length of 10 inches, giving half an inch to a degree F., and carefully graduated to tenths of a degree, so that they can be read to hundredths, corresponding to single degrees of the heat-carrier in the normal use of the instrument.

For the determination of the highest temperatures, up closely to 2,900° F., it will be convenient to have thermometers of greater range, say 32° to 82° F., 50° in a length of 12.5 inches, or a quarter of an inch to a degree F., also graduated to tenths, or at the least, to fifths of a degree. Such thermometers will be about 17 inches long.

It is very satisfactory to have _two_ instruments and a good outfit of thermometers and heat-carriers, in order to take duplicate observations for mutual verification and detection of errors.

HEAT CARRIERS.

For these platinum is greatly to be preferred to any other known substance. Its rather high cost is the only objection to its use. Its heat capacity is low, by weight, but its specific gravity is great, and sufficient capacity can be obtained in moderate bulk, while its high conductivity tends to shorten the duration of each experiment or observation. A convenient outfit for each instrument consists of three balls, hammered to a spherical form, one 1.1385 inches diameter, weighing 4,200 grains=0.6 pound avoirdupois; one 0.9945 inch diameter, weighing 2,800 grains=0.4 pound; and one 0.7894 inch diameter, weighing 1,400 grains=0.2 pound.

These can be obtained at 1-2/3 cents per grain, and will cost, respectively, $70.00, $46.67, and $23.33, and collectively, $140.00. At the assumed specific heat of Pt=0.0333+, the heat capacity of the respective balls will be 1/100, 1/150, and 1/300 of 2 pounds of cold water, and the two smaller balls used together will be equal to the larger one. Corrections for varying specific heat of platinum may be conveniently made by the tables given in a previous article.[1] Corrections for varying specific heat of water are less important, but may be made by the following table:

_Temperatures, Fahrenheit, and Corresponding Number of British Thermal Units Contained in Water from Zero Fahrenheit_.

_______________________________________________________________ Deg | B.t.u. || Deg | B.t.u. || Deg | B.t.u. || Deg | B.t.u. | ----+--------++-----+--------++-----+---------++-----+---------+ 32 | 32.000 || 57 | 57.007 || 82 | 82.039 || 107 | 107.101 | 33 | 33.000 || 58 | 58.007 || 83 | 83.041 || 108 | 108.104 | 34 | 34.000 || 59 | 59.008 || 84 | 84.043 || 109 | 109.107 | 35 | 35.000 || 60 | 60.009 || 85 | 85.045 || 110 | 110.110 | 36 | 36.000 || 61 | 61.010 || 86 | 86.047 || 111 | 111.113 | 37 | 37.000 || 62 | 62.011 || 87 | 87.049 || 112 | 112.117 | 38 | 38.000 || 63 | 63.012 || 88 | 88.051 || 113 | 113.121 | 39 | 39.001 || 64 | 64.013 || 89 | 89.053 || 114 | 114.125 | 40 | 40.001 || 65 | 65.014 || 90 | 90.055 || 115 | 115.129 | 41 | 41.001 || 66 | 66.015 || 91 | 91.057 || 116 | 116.133 | 42 | 42.001 || 67 | 67.016 || 92 | 92.059 || 117 | 117.137 | 43 | 43.001 || 68 | 68.018 || 93 | 93.061 || 118 | 118.141 | 44 | 44.002 || 69 | 69.019 || 94 | 94.063 || 119 | 119.145 | 45 | 45.002 || 70 | 70.020 || 95 | 95.065 || 120 | 120.149 | 46 | 46.002 || 71 | 71.021 || 96 | 96.068 || 121 | 121.153 | 47 | 47.002 || 72 | 72.023 || 97 | 97.071 || 122 | 122.157 | 48 | 48.003 || 73 | 73.024 || 98 | 98.074 || 123 | 123.161 | 49 | 49.003 || 74 | 74.036 || 99 | 99.077 || 124 | 124.165 | 50 | 50.003 || 75 | 75.027 || 100 | 100.080 || 125 | 125.169 | 51 | 51.004 || 76 | 76.029 || 101 | 101.083 || 126 | 126.173 | 52 | 52.004 || 77 | 77.030 || 102 | 102.086 || 127 | 127.177 | 53 | 53.005 || 78 | 78.032 || 103 | 103.089 || 128 | 128.182 | 54 | 54.005 || 79 | 79.034 || 104 | 104.092 || 129 | 129.187 | 55 | 55.006 || 80 | 80.036 || 105 | 105.095 || 130 | 130.192 | 56 | 56.006 || 81 | 81.037 || 106 | 106.098 || 131 | 131.197 | ----+--------++-----+--------++-----+---------++-----+---------+

[Footnote 1: _Journal_ for August, pp. 97, 98, and errata in _Journal_ for September, p. 172.]

A composite heat-carrier, of iron covered with platinum, answers well for temperatures up to about 1,500° F. A ball of wrought iron 0.88 inch diameter will weigh 700 grains, and a capsule of platinum spun over it 0.048 inch thick, making the outside diameter 0.976+ inch, will also weigh 700 grains. Upon the assumption of 0.0333+ for the specific heat of Pt and 0.1666+ for that of Fe, the composite ball will have a heat capacity equal to that of 4,200 grains of Pt, and equal to 0.01 of that of 2 pounds of cold water. A patch, about 0.35 inch diameter, has to be put in to close the orifice where the Pt capsule is spun together, and a slight stain will show itself at the joint around this patch, from oxidation of the iron, but the latter will be pretty effectually protected. Difference of expansion, which will not exceed 0.007 inch in diameter, will not endanger the capsule of Pt. The interruption of conductivity at the surface contact of the two metals makes the process of heating and cooling a little slower, but not noticeably so.

Such composite balls can be obtained for $20 each, $50 less than the cost of an equivalent ball of solid platinum, which is preferable in all but cost. Iron balls could be used for a few crude determinations. Cast iron varies too much in composition, and wrought iron oxidizes rapidly. While the oxide adheres it gains in weight, and when scales fall off it loses; and the specific heat of the oxide differs from that of metallic iron. Whatever metal is used, care must be taken to apply the appropriate tabular correction for PtFe, or Pt and Fe.

MANIPULATION.

Small graphite crucibles with covers, as shown in section, in Fig. 2, serve to guard against losing the ball, to handle it by when hot, and to protect it against loss of heat during transmission from the fire to the pyrometer. To guard against overturning the crucibles, moulded firebrick should be provided to receive them, two crucibles being put into one brick, in the same exposure, whenever great accuracy is desired, each serving as a check on the other, and their mean being likely to be more nearly correct than either one if they differ. The firebrick cover is occasionally useful to retard cooling, if, by reason of local obstructions, some little delay is unavoidable in transferring the balls from the fire to the water of the pyrometer. With convenient arrangements, this may be done in three seconds. After observing the temperature of the water, make ready for the immersion of the heat carrier by raising the agitator until a space of only about 1.5 of an inch is left between its rim and the cover. An instant before putting in the heat carrier--"pouring" it from the crucible--lift the cover and agitator both together, so that the rim of the latter is level with the sloping top of the instrument. The agitator then receives the hot ball without shock, and no harm is done. If the ball goes below the agitator, it is likely to injure the bottom of the cup. If, on taking the temperature of the water before the immersion of the heat carrier, any change is observed, either rising or falling, the direction and rate of such change, and the exact interval of time between the last recorded observation and the immersion, should be noted, in order to determine the exact temperature of the water at the instant of immersion. The temperature of the water will continue to rise as long as the heat carrier gives out heat faster than the cell loses it. The rise will grow gradually slower until it ceases, and the maximum can be very accurately determined. Examples of the mode of using the tables, and of determining the true temperature of the heat carrier at the instant of immersion from the observations with the instrument, are given in the table on pages 170 and 171 of this Journal for September. A method of using the tables, by which a closer approximation to the true temperature may be reached, will be pointed out in a subsequent article.

DETERMINATION OF THE CALORIFIC CAPACITY OF THE METALS OF THE PYROMETER, in terms of water, i.e., in British thermal units.

First. Weigh the cup, or cell, the lower plate of the cover and the metallic portion of the agitator, and compute their heat-capacity by the specific heat of the respective metals. Compute also the heat capacity of the thermometer; or, if it be long, of so much of it as is found to share nearly the temperature of the immersed portion. The result will be a minimum--indeed, in so small a vessel the inevitable loss by conduction and radiation will amount to more than one-third as much as the simple heat capacity of the metals.[1] The total must be ascertained by an application of the method of mixture. Ascertain the temperature of the interior of the instrument simply; pour in quickly but carefully a known quantity of water, say about two pounds, of known temperature, say about 100° F., and ascertain the temperature as soon after pouring as mixing can be properly performed. But a correction is necessary for loss of heat in the act of pouring. To ascertain the amount of this correction prepare a bath of tepid water, and bring all parts of the instrument--outside, inside, and interior portions, together with the vessel to pour from--exactly to one common, carefully ascertained temperature. Now take two pounds of the water and pour it into the cell in the same manner as before. Exposure of so thin a stream on two surfaces to the air of the room will produce a certain degree of refrigeration in the water, which is supposed to be warmer than the air, say at about 160° F. This effect will be due to conduction, by contact with the air, to radiation, and to evaporation; and by so much the refrigeration observed in mixing is to be diminished.

[Footnote 1: In our case the heat-capacity, thermometer included, was 0.0757; total, 0.1053; radiation, etc., 0.0296. Respectively, 71.9 per cent, and 28.1 per cent. of the total.]

Four experiments, carefully conducted, gave the following results:

Loss of temperature by pouring at 170° F., 0.81°, 0.86°, 1.00°, and 1.07° F.; mean, 0.935° F.

The following are values of the calorific capacity of my pyrometers, that is, of those parts of each which share directly the temperature of the inclosed water, including the thermometer to be used with the instrument, and the heat communicated to the eider-down and otherwise lost during an observation, expressed in decimals of a British thermal unit, or in decimals of a pound of cold water:

0.1048, 0.1052, 0.1077, 0.1008, 0.1028, and 0.1104.

Mean 0.1053 = 0 lb. 1 oz. 11 drms.
Add water 1.8947 = 1 " 14 " 4 "
------ - -- --
2.0000 = 2 " 0 " 0 "

This was the value used. The instrument, being put on delicate coin scales and counterbalanced, weights equal to 1.8947 lb. avoirdupois = 1 lb. 14 oz. 5 drms., were added to the counterbalancing weights, and cold water was poured in until the scales again balanced.

The pyrometer with its contained water was then just equal in heating capacity, while the temperature was not above 38° F. to two pounds of cold water. The two instruments were sensibly alike, but were numbered No. 1 and No. 2, and at each observation the one used was noted.

The process of preparation and testing appears long and tedious, and is indeed somewhat so; but the instruments once well made are durable, convenient in use, and with care reasonably accurate.

Compared with mercurial thermometers between 212° and 600° F., I believe them to be much more accurate, although less convenient.

For a range of temperatures from 212° to 900° F. they are certainly more trustworthy than anything save an air thermometer of suitable construction; and for all temperatures from 800° to 900° F. up nearly to the melting point of platinum they are without a rival, so far as I know.

For some situations the ball can best be inserted in the fire or other situation where an observation is desired, and withdrawn for immersion by means of long, slender tongs, with jaws resembling bullet moulds.

A word about the melting point of platinum. My balls certainly began to melt below 2,950° F., but I am by no means sure that they do not contain any silver, although their specific gravity gives assurance that they are at least nearly pure.--_Franklin Journal_.

* * * * *

LOCOMOTIVE PAINTING.

[Footnote: A paper read before the Master Car Painters' Association, Chicago, September, 1883.]

By JOHN S. ATWATER.

The subject of locomotive painting has been pretty well discussed at the former meetings of the association, and we have heard many excellent suggestions regarding the use of oils, mineral paints, and leads from gentlemen of long experience. But as the secretary has invited a display of my ignorance I will endeavor to explain as clearly as possible the methods I pursue, which, though not new or original, have been productive of good results.

If time enough can be had we can prime with oil alone, or in connection with the leads or minerals, and be sure of durability; but in these days of "lightning speed," "lightning illuminations," and "lightning painting," we must look about for something with "chain lightning" in it, which, unlike the lightning, will remain bright and stick after it strikes. We all have to paint according to the time and the facilities we have for doing the work.

The scale on iron or steel is the only serious trouble which the painter has to contend with. Rust can be removed or utilized with the oil, making a good paint, but unless time can be given it is better to remove the rust.

If possible let tanks get thoroughly rusted, then scrape off scale and rust with files sharpened to a chisel edge, rub down large surfaces with sandstone, and use No. 3 emery cloth between rivet heads, etc., then wash off with turpentine. This will give you a good solid surface to work upon.

For priming I use 100 pounds white lead (in oil), 10 pounds dry red lead, 13 pounds Prince's metallic, 8 quarts boiled oil, 2 quarts varnish, 6 quarts turpentine, and grind in the mill, as it mixes it thoroughly with less waste. I mix about 250 pounds at a time (put into kegs and draw off as wanted through faucets).

This _o-le-ag-in-ous_ compound can be worked both ways, quickly by adding japan, slower by adding oil, and reduce to working consistency with turpentine.

Without the oil or japan it will dry hard on wrought iron in about seven days, on castings in about four days. When dry putty with white-lead putty, thinned with varnish and turpentine, and knifed in with a "broad-gauge" putty knife. Next day sandpaper and apply first coat rough-stuff, which is, equal parts, in bulk, white lead and "Reno's umber," mixed "stiff" with equal parts japan and rubbing varnish, and thin with turpentine. Next morning, second coat rough-stuff, made with Reno's umber, fine pumice stone, japan, and turpentine. At 1 o'clock P.M. put on guide coat for the benefit of the small boys, which is rough-stuff No. 2, darkened with lamp-black and very thin. The addition of fine pumice to rough-stuff No. 2 encourages the boys in rubbing, and prevents the blockstone from clogging.

By the time the last end of the tank is painted the first end is ready for rubbing, though it is better to stand until next day.

After rubbing sandpaper and put on very thin coat of varnish and turpentine (about equal parts). This soaks into the filling, hardening it and making a close, smooth, elastic surface, leaving no brush marks and being more durable than a _quick_-drying lead. This can be rubbed with fine sandpaper or hair to take off gloss, and colored the next morning, but it is better to remain 24 hours before coloring.

Upon this surface an "all japan color" would, before night, resemble a map of the war in Egypt, but by adding varnish and a very little raw oil to the "japan color," making it of the same nature as the under surface, will prevent cracking.

If I sandpaper in the morning, I put on first-coat color before noon. Second ditto afternoon, and varnish with rubbing varnish that night; rub down, stripe and letter next day, though I consider it better to stripe and letter on the color, and varnish with "wearing body varnish."

The tank is then ready for mounting. When mounted I paint trucks and woodwork, two coats lead, color, "color and varnish," and finish the whole with "wearing body varnish." Time, from 14 to 16 days.

On cabs I use the same priming as on tanks, let stand five days, putty nail holes and "plaster putty" hard wood, and give two coats lead, mixed as follows: 100 pounds keg lead, 19 pounds Reno's umber, 3½ quarts japan, 1½ quarts varnish, 6 quarts turpentine. I call this "No. 2 lead," and allow 24 hours between coats, then apply a coat of No. 2 "rough stuff" at 7 A.M. Rub down at 10 A.M. two coats color, and varnish before 6 P.M. Striped and lettered next day and finished on the following day if it is not taken away from me, and put on the engine. Time, eleven days. Can be done in five days.

On castings, same priming, putty and "No. 2 lead" if time is allowed. I use rough-stuff No. 2 on all flat places, rub down and give two coats of No. 2 lead. Also painting inside of all castings, and sheet iron casings; and inside of boiler jacket, with "Prince's metallic."

All castings I get ready for color before they are put on the locomotive, except such as have to be filed or fitted on outside edges. As there is very little time given to finish a locomotive after the machinists get through, I usually finish it _the day before it is done_.

As a sample (one of many), an 8--17--C. locomotive boiler tested Saturday afternoon, August 12, boiler painted, with 120 pounds steam on, wheels put under, boiler covered, cab put on, and finished Monday, August 14, at midnight (did not work Sunday); primed, puttied, colored, lettered, and varnished same day. After 10 o'clock at night the painters have a chance, and it is their glorious privilege to work until morning. The machinists have all the time there is, the painters have what is left.

So much for the ordinary way. For a quicker method of painting tanks I send a sample marked No. 1. Time, including first coat varnish, five days. Priming, 1 pound Reno's umber to 2 quarts pellucedite; two coats rough-stuff, composed of umber and pellucedite, rubbed down, and thin coat of pellucedite; one coat drop black, one coat rubbing varnish; exposed to weather (southeasterly exposure near salt water) March 12, 1879; revarnished one coat, finishing September 1, 1879; remained out until March 22, 1880. Total exposure, one year and one and a half weeks; thrown around the shop until August, 1882; has been painted three years and six months. This is not a sample of good work, but of quick and rough painting. Considering the time and usuage it has experienced it has stood much better than I expected, though I cannot safely recommend that kind of painting when any other can be followed.

Sample No. 3--Time, including two coats varnish, 14 days. Painted as described in first part of this article; exposed in same places as No. 1, April 3, 1880; total exposure, six months; has been painted two years and five months.

The above are not exactly "Thoughts on Locomotive Painting." What my thoughts are would require several dictionaries to express; but that is owing, not to the kind of work, but having to produce certain results in a time that will not insure good, durable work.