Chapter II: Part 2

The kilns were formerly roofed over with rough boards to protect the masonry from the weather, but as no special advantage was found to result from so doing, since of late years they have been made water-proof, the practice has been discontinued.

The wood used is cut about one and a fifth meters long. The diameter is not considered of much importance, except in so far as it is desirable to have it as nearly uniform as possible. When most of the wood is small, and only a small part of it is large, the large pieces are usually split, to make it pack well. It has been found most satisfactory to have three rows of vents around the kiln, which should be provided with a cast-iron frame reaching to the inside of the furnace. The vents near the ground are generally five inches high--the size of two bricks--and four inches wide--the width of one--and the holes are closed by inserting one or two bricks in them. They are usually the size of one brick, and larger on the outside than on the inside. These holes are usually from 0.45 m. to 0.60 m. apart vertically, and from 0.80 m. to 0.90 m. apart horizontally. The lower vents start on the second row of the brickwork above the foundation, and are placed on the level with the floor, so that the fire can draw to the bottom. There is sometimes an additional opening near the top to allow of the rapid escape of the smoke and gas at the time of firing, which is then closed, and kept closed until the kiln is discharged. This applies mostly to the best types of conical kilns. In the circular and conical ones the top charging door is sometimes used for this purpose. Hard and soft woods are burned indifferently in the kilns. Hard-wood coal weighs more than soft, and the hard variety of charcoal is usually preferred for blast furnaces, and for such purposes there is an advantage of fully 33-1/3 per cent. or even more in using hard woods. For the direct process in the bloomaries, soft-wood charcoal is preferred. It is found that it is not usually advantageous to build kilns of over 160 to 180 cubic meters in capacity. Larger furnaces have been used, and give as good a yield, but they are much more cumbersome to manage. The largest yield got from kilns is from 50 to 60 bushels for hard wood to 50 for soft wood. The average yield, however, is about 45 bushels. In meilers, two and a half to three cords of wood are required for 100 bushels, or 30 to 40 bushels to the cord. The kiln charcoal is very large, so that the loss in fine coal is very much diminished. The pieces usually come out the whole size, and sometimes the whole length of the wood.

The rectangular kilns were those which were formerly exclusively in use. They are generally built to contain from 30 to 90 cords of wood. The usual sizes are given in the table below:

1 2 3 4
Length 50 40 40 48
Width 12 15 14 17
Height 12 15 18 18
Capacity, in cords 55 70 75 90

1 and 2. Used in New England. 3. Type of those used in Mexico. 4. Kiln at Lauton, Mich.

The arch is usually an arc of a circle. A kiln of the size of No. 4, as constructed at the Michigan Central Iron Works, with a good burn, will yield 4,000 bushels of charcoal.

The vertical walls in the best constructions are 12 to 13 feet high, and 1-½ brick thick, containing from 20 to 52 bricks to the cubic foot of wall. To insure sufficient strength to resist the expansion and contraction due to the heating and cooling, they should be provided with buttresses which are 1 brick thick and 2 wide, as at Wassaic, New York; but many of them are built without them, as at Lauton, Michigan, as shown in the engraving. In both cases they are supported with strong braces, from 3 to 4 feet apart, made of round or hewn wood, or of cast iron, which are buried in the ground below, and are tied above and below with iron rods, as in the engraving, and the lower end passing beneath the floor of the kiln. When made of wood they are usually 8 inches square or round, or sometimes by 8 inches placed edgewise. They are sometimes tied at the top with wooden braces of the same size, which are securely fastened by iron rods running through the corners, as shown. When a number of kilns are built together, as at the Michigan Central Iron Works, at Lauton, Michigan, shown in the plan view, only the end kilns are braced in this way. The intermediate ones are supported below by wooden braces, securely fastened at the bottom. The roof is always arched, is one brick, or eight inches, thick, and is laid in headers, fourteen being used in each superficial foot. Many of the kilns have in the center a round hole, from sixteen to eighteen inches in diameter, which is closed by a cast iron plate. It requires from 35 M. to 40 M. brick for a kiln of 45 cords, and 60 M. to 65 M. for one of 90 cords.

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The belief that population in the West Indies is stationary is so far from accurate that, as Sir Anthony Musgrave points out, it is increasing more rapidly than the population of the United Kingdom. The statistics of population show an increase of 16 per cent. on the last decennial period, while the increase in the United Kingdom in the ten years preceding the last census was under 11 per cent. This increase appears to be general, and is only slightly influenced by immigration. "The population of the West Indies," adds Sir A. Musgrave, "is now greater than that of any of the larger Australian colonies, and three times that of New Zealand."

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HEAT DEVELOPED IN FORGING.

M. Tresca has lately presented to the Academy of Sciences some very interesting experiments on the development and distribution of heat produced by a blow of the steam hammer in the process of forging. The method used was as follows: The bar was carefully polished on both sides, and this polished part covered with a thin layer of wax. It was then placed on an anvil and struck by a monkey of known weight, P, falling from a height, H. The faces of the monkey and anvil were exactly alike, and care was taken that the whole work, T = PH, should be expended upon the bar. A single blow was enough to melt the wax over a certain zone; and this indicated clearly how much of the lateral faces had been raised by the shock to the temperature of melting wax. The form of this melted part could be made to differ considerably, but approximated to that of an equilateral hyperbola. Let A be the area of this zone, b the width of the bar, d the density, C the heat capacity, and t-t0 the excess of temperature of melting wax over the temperature of the air. Then, assuming that the area, A, is the base of a horizontal prism, which is everywhere heated to the temperature, t, the heating effect produced will be expressed by

Ab x d x C(t-t0)

Multiplying this by 425, or Joule's equivalent for the metrical system, the energy developed in heat is given by

T1 = 425 AbdC(t-t0).

Dividing T1 by T, we obtain the ratio which the energy developed in heat bears to the total energy of the blow.

With regard to the form of the zone of melting, it was found always to extend round the edges of the indent produced in the bar by the blow. We are speaking for the present of cases where the faces of the monkey and anvil were sharp. On the sides of the bar the zone took the form of a sort of cross with curved arms, the arms being thinner or thicker according to the greater or less energy of the shock. These forms are shown in Figs. 1 to 6. It will be seen that these zones correspond to the zones of greatest sliding in the deformation of a bar forged with a sharp edged hammer, showing in fact that it is the mechanical work done in this sliding which is afterward transformed into heat.

With regard to the ratio, above mentioned, between the heat developed and the energy of the blow, it is very much greater than had been expected when the other sources of loss were taken into consideration. In some cases it reached 80 per cent., and in a table given the limits vary for an iron bar between 68.4 per cent. with an energy of 40 kilogram-meters, and 83.6 per cent. with an energy of 90 kilogram-meters. With copper the energy is nearly constant at 70 per cent. It will be seen that the proportion is less when the energy is less, and it also diminishes with the section of the bar. This is no doubt due to the fact that the heat is then conducted away more rapidly. On the whole, the results are summed up by M. Tresca as follows:

(1) The development of heat depends on the form of the faces and the energy of the blow.

(2) In the case of faces with sharp edges, the process described allows this heat to be clearly indicated.

(3) The development of heat is greatest where the shearing of the material is strongest. This shearing is therefore the mechanical cause which produces the heating effect.

(4) With a blow of sufficient energy and a bar of sufficient size, about 80 per cent. of the energy reappears in the heat.

(5) The figures formed by the melted wax give a sort of diagram, showing the distribution of the heat and the character of the deformation in the bar.

(6) Where the energy is small the calculation of the percentage is not reliable.

So far we have spoken only of cases where the anvil and monkey have sharp faces. Where the faces are rounded the phenomena are somewhat different. Figs. 7 to 12 give the area of melted wax in the case of bars struck with blows gradually increasing in energy. It will be seen that, instead of commencing at the edges of the indent, the fusion begins near the middle, and appears in small triangular figures, which gradually increase in width and depth until at last they meet at the apex, as in Fig. 12. The explanation is that with the rounded edges the compression at first takes place only in the outer layers of the bar, the inner remaining comparatively unaffected. Hence the development of heat is concentrated on these outer layers, so long as the blows are moderate in intensity. The same thing had already been remarked in cases of holes punched with a rounded punch, where the burr, when examined, was found to have suffered the greatest compression just below the punch. With regard to the percentage of energy developed as heat, it was about the same as in the previous experiments, reaching in one case, with an iron bar and with an energy of 110 kilogram-meters, the exceedingly high figure of 91 per cent. With copper, the same figure varied between 50 and 60 per cent.--_Iron_.

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A NOVEL PROPELLER ENGINE.

By Prof. C.W. MacCord.

The accompanying engravings illustrate the arrangement of a propeller engine of 20 inch bore and 22 inch stroke, whose cylinder and valve gear were recently designed by the writer, and are in process of construction by Messrs. Valk & Murdoch, of Charleston, S.C.

In the principal features of the engine, taken as a whole, as will be perceived, there is no new departure. The main slide valve, following nearly full stroke, is of the ordinary form, and reversed by a shifting link actuated by two eccentrics, in the usual manner; and the expansion valves are of the well known Meyer type, consisting of two plates on the back of the main valve, driven by a third eccentric, and connected by a right and left handed screw, the turning of which alters the distance between the plates and the point of cutting off.

The details of this mechanism, however, present several novel features, of which the following description will be understood by reference to the detached cuts, which are drawn upon a larger scale than the general plan shown in Figs. 1 and 2.

The first of these relates to the arrangement of the right and left handed screw, above mentioned, and of the device by which it is rotated.

Usually, the threads, both right handed and left handed, are cut upon the cut-off valve stem itself, which must be so connected with the eccentric rod as to admit of being turned; and in most cases the valve stem extends through both ends of the steam chest, so that it must both slide endwise and turn upon its axis in two stuffing boxes, necessarily of comparatively large size.

All this involves considerable friction, and in the engine under consideration an attempt has been made to reduce the amount of this friction, and to make the whole of this part of the gear neater and more compact, in the following manner:

Two small valve stems are used, which are connected at their lower ends by a crosstail actuated directly by the eccentric rod, and at their upper ends by a transverse yoke. This yoke, filling snugly between two collars formed upon a sleeve which it embraces, imparts a longitudinal motion to the latter, while at the same time leaving it free to rotate.

This sleeve has cut upon it the right and left handed screws for adjusting the cut-off valves; and it slides freely upon a central spindle which has no longitudinal motion, but, projecting through the upper end of the valve chest, can be turned at pleasure by means of a bevel wheel and pinion. The rotation of the spindle is communicated to the sleeve by means of two steel keys fixed in the body of the latter and projecting inwardly so as to slide in corresponding longitudinal grooves in the spindle.

Thus the point of cutting off is varied at will while the engine is running, by means of the hand wheel on the horizontal axis of the bevel pinion, and a small worm on the same axis turns the index, which points out upon the dial the distance followed. These details are shown in Figs. 3, 4, and 5; in further explanation of which it may be added that Fig. 3 is a front view of the valve chest and its contents, the cover, and also the balance plate for relieving the pressure on the back of the main valve (in the arrangement of which there is nothing new), being removed in order to show the valve stems, transverse yoke, sleeve, and spindle above described. Fig. 4 is a longitudinal section, and Fig. 5 is a transverse section, the right hand side showing the cylinder cut by a plane through the middle of the exhaust port, the left hand side being a section by a plane above, for the purpose of exhibiting more clearly the manner in which the steam is admitted to the valve chest; the latter having no pipes for this service, the steam enters below the valve, at each end of the chest, just as it escapes in the center.

The second noteworthy feature consists in this: that the cut-off eccentric is not keyed fast, as is customary when valve gear of this kind is employed, but is loose upon the shaft, the angular position in relation to the crank being changed when the engine is reversed; two strong lugs are bolted on the shaft, one driving the eccentric in one direction, the other in the opposite, by acting against the reverse faces of a projection from the side of The eccentric pulley.

The loose eccentric is of course a familiar arrangement in connection with poppet valves, as well as for the purpose of reversing an engine when driving a single slide valve. Its use in connection with the Meyer cut-off valves, however, is believed to be new; and the reason for its employment will be understood by the aid of Fig. 6.

For the purposes of this explanation we may neglect the angular vibrations of the connecting rod and eccentric rod, considering them both as of infinite length. Let O be the center of the shaft; let L O M represent the face of the main valve seat, in which is shown the port leading to the cylinder; and let A be the edge of the main valve, at the beginning of a stroke of the piston. It will then be apparent that the center of the eccentric must at that instant be at the point, C, if the engine turn to the left, as shown by the arrow, and at G, if the rotation be in the opposite direction; C and G then may be taken as the centers of the "go-ahead" and the "backing" eccentrics respectively, which operate the main valve through the intervention of the link.

Now, in each revolution of the engine, the cut-off eccentric in effect revolves in the same direction about the center of the main eccentric. Consequently, we may let R C S, parallel to L O M, represent the face of the cut-off valve seat, or, in other words, the back of the main valve, in which the port, C N, corresponds to one of those shown in Fig. 4; and the motion of the cut-off valve over this seat will be precisely, the same as though it were driven directly by an eccentric revolving around the center, C.

In determining the position of this eccentric, we proceed upon the assumption that the best results will be effected by such an arrangement that when cutting off at the earliest point required, the cut-off valve shall, at the instant of closing the port, be moving over it at its highest speed. And this requires that the center of the eccentric shall at the instant in question lie in the vertical line through C.

Next, the least distance to be followed being assigned, the angle through which the crank will turn while the piston is traveling that distance is readily found; then, drawing an indefinite line C T, making with the vertical line, G O, an angle, G C T. equal to the one thus determined, any point upon that line may be assumed as the position of the required center of the cut-off eccentric, at the beginning of the stroke.

But again, in order that the cut-off may operate in the same manner when backing as when going ahead, this eccentric must be symmetrically situated with respect to both C and G; and since L O M bisects and is perpendicular to G C, it follows that if the cut-off eccentric be fixed on the shaft, its center must be located at H, the intersection of C T with L M. This would require the edge of the cut-off valve at the given instant to be at Q, perpendicularly over H; and the travel over the main valve would be equal to twice C H, the virtual lever arm of the eccentric, the actual traverse in the valve chest being twice O H, the real eccentricity.

This being clearly excessive, let us next see what will occur if the lever arm, CH, be reduced as in the diagram to CK. The edge of the cut-off valve will then be at N; it instantly begins to close the port. CN, but not so rapidly as the main valve opens the port, AB.

The former motion increases in rapidity, while the latter decreases; therefore at some point they will become equal in velocity, and the openings of the two ports will be the same; and the question is, Will this maximum effective port area give a sufficient supply of steam?

This diagram is the same as the one actually used in the engine under consideration, in which it was required to follow a minimum distance of 5 inches in the stroke of 22. Under these conditions it is found that the actual port opening for that point of cutting off is three-fifths of that allowed when following full stroke, whereas the speed of the piston at the time when this maximum opening occurs is less than half its greatest speed.

This, it would seem, is ample; but we now find the eccentric, K, no longer in the right position for backing; when the engine is reversed it ought to be at, P, the angle, POL, being equal to the angle, KOL. By leaving it free, therefore, to move upon the shaft, by the means above described, through the angle, KOP, the desired object is accomplished. The real eccentricity is now reduced in the proportion of OK to OH, while the lengths of the cut-off valves, and what is equally important, their travel over the back of the main valve, are reduced in the proportion of CK to CH, in this instance nearly one-half; a gain quite sufficient to warrant the adoption of the expedient.

The third, and perhaps the most notable, peculiarity is the manner of suspending and operating the main link. As before stated, this link is used only for reversing, and is therefore always in "full gear" in one direction or the other; and the striking feature of the arrangement here used is that, whether going ahead or backing, there is _no slipping of the link upon the link block_.

The link itself is of the simplest form, being merely a curved flat bar, L, in which are two holes, A and B (Fig. 7), by which the link is hung upon the pins, which project from the sides of the eccentric rods at their upper ends.

This is most clearly shown in Fig. 8, which is a top view of the reversing gear. The link block is a socket, open on the side next to the eccentric rods, but closed on the side opposite, from which projects the journal, J, as shown in Fig. 9, which is a vertical section by the plane, XY. This journal turns freely in the outer end of a lever, M, which transmits the reciprocating motion to the valve, through the rock-shaft, O, and another lever, N. Connected with the lever, M, by the bridge-piece, K, and facing it, is a slotted arm, G, as shown in the end view, Fig. 10. The center line of this slot lies in the plane which contains the axes of the journal, J, and of the shaft, O.

A block, E, is fitted to slide in the slotted arm, G; and in this block is fixed a pin, P. A bridle-rod, R, connects P with the pin, A, of one of the eccentric-rods, prolonged for that purpose as shown in Fig. 8; and a suspension-rod, S, connects the same pin, P, with the upper end of the reversing lever, T, which is operated by the worm and sector. The distance, JO, in Fig. 10, or in other words the length of the lever, M, is precisely equal to the distance, AB, in Fig. 7, measured in a right line; and the rods, R and S, from center to center of the eyes, are also each of precisely this same length. Further, the axis about which the reversing lever, T, vibrates is so situated that when that lever, as in Fig 11, is thrown full to the left, the pin in its upper end is exactly in line with the rock-shaft, O.

When the parts are in this position, the suspension-rod, S, the arm, G, and the lever, M, will be as one piece, and their motions will be identical, consisting simply of vibration about the axis of the rock-shaft, O. The motion of the lever, M, is then due solely to the pin, B, which is in this case exactly in line with the journal, J, so that the result is the same as though this eccentric rod were connected directly to the lever; and the pin, P, being also in line with B and J, and kept so by the suspension-rod, S, it will be seen that the bridle-rod, R, will move with the link, L, as though the two were rigidly fastened together.

When the reversing lever, T, is thrown full to the right, as in Fig. 12, the pin, P, is drawn to the inner end of the slot in the arm, G, and is thus exactly in line with the rock-shaft, O. The suspension-rod, S, will, therefore, be at rest; but the pin, A, will have been drawn, by the bridle-rod, R, into line with the journal, J, and the bridle-rod itself will now vibrate with the lever, M, whose sole motion will be derived from the pin, A.

There is, then, no block slip whatever when the link thus suspended and operated is run in "full gear," either forward or backward.

If this arrangement be used in cases where the link is used as an expansion device, there will be, of course, some block slip while running in the intermediate gears. But even then, it is to be observed that the motion of the pin, A, relatively to the rocker arm is one of vibration about the moving center, J; and its motion relatively to the sliding block, E, is one of vibration about the center, P, whose motion relatively to E is a small amount of sliding in the direction of the slot, due to the fact that the rocker arm itself, which virtually carries the block, E, vibrates about O, while the suspension-rod, S, vibrates about another fixed center. It will thus be seen that, finally, the block slip will be determined by the difference in curvature of arcs _which curve in the same direction_, whether the engine be running forward or backward; whereas in the common modes of suspension the block slip in one direction is substantially the half sum of the curvatures of two arcs curving in opposite directions.

Consequently it would appear that the average action of the new arrangement would be at least equal to that of the old in respect to reducing the block slip when running in the intermediate gears, while in the full gears it entirely obviates that objectionable feature.

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THE NEW RUSSIAN TORPEDO BOAT, THE POTI.

The Russian government has just had built at the shipyards of Mr. Normand, the celebrated Havre engineer, a torpedo boat called the Poti, which we herewith illustrate. This vessel perceptibly differs from all others of her class, at least as regards her model. Her extremities, which are strongly depressed in the upperworks, and the excessive inclination of her sides, give the boat as a whole a certain resemblance to the rams of our navy, such as the Taureau and Tigre.

A transverse section of the Poti approaches an ellipse in shape. Her water lines are exceedingly fine, and, in point of elegance, in no wise cede to those of the most renowned yachts. The vessel is entirely of steel, and her dimensions are as follows: Length, 28 meters; extreme breadth, 3.6 meters; depth, 2.5 meters; draught, 1.9 meters; displacement, 66 tons. The engine, which is a compound one, is of 600 H.P. The minimum speed required is 18 knots, or 33-34 meters, per hour, and it will probably reach 40 kilometers.

The vessel will be armed with 4 Whitehead torpedoes of 5.8 m., and 2 Hotchkiss guns of 40 cm. Her supply of coal will be sufficient for a voyage of 1000 nautical miles at a speed of 11 knots.--_L'Illustration_.

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A NEW STEAMER PROPELLED BY HYDRAULIC REACTION.

The oar, the helix, and the paddle-wheel constitute at present the means of propulsion that are exclusively employed when one has recourse to a motive power for effecting the propulsion of a boat. The sail constitutes an entirely different mode, and should not figure in our enumeration, considering the essentially variable character of the force utilized.

In all these propellers, we have only an imitation, very often a rude one, of the processes which nature puts in play in fishes and mollusks, and the mode that we now wish to make known is without contradiction that which imitates these the best.

Hydraulic propulsion by reaction consists, in principle, in effecting a movement of boats, by sucking in water at the bow and forcing it out at the stern. This is a very old idea. Naturalists cite whole families of mollusks that move about in this way with great rapidity. It is probable that such was the origin of the first idea of this mode of operating. However this may be, as long ago as 1661 a patent was taken out in England, on this principle, by Toogood & Hayes. After this we find the patents of Allen (1729) and Rumsay (1788). In France, Daniel Bernouilli presented to the Académic des Sciences a similar project during the last century.

Mr. Seydell was the first to build a vessel on this principle. This ship, which was called the Enterprise, was of 100 tons burden, and was constructed at Edinburgh for marine fishery. The success of this was incomplete, but it was sufficient to show all the advantage that could be got from the idea. Another boat, the Albert, was built at Stettin, after the same type and at about the same epoch; and the question was considered of placing a reaction propeller upon the Great Eastern.

About 1860 the question was taken up again by the house of Cokerill de Seraing, which built the Seraing No. 2, that did service as an excursion boat between Liége and Seraing. The propeller of this consisted of a strong centrifugal pump, with vertical axis, actuated by a low pressure engine. This pump sucked water into a perforated channel at the bottom of the boat, and forced it through a spiral pipe to the propelling tubes. These latter consisted of two elbowed pipes issuing from the sides of the vessel and capable of pivoting in the exhaust ports in such a way as to each turn its mouth downward at will, backward or forward. The water expelled by the elbowed pipes reacted through pressure, as in the hydraulic tourniquet of cabinets of physics, and effected the propulsion of the vessel. Upon turning the two mouths of the propelling tubes backward, the boat was thrust forward, and, when they were turned toward the front, she was thrust backward. When one was turned toward the front and the other toward the stern, the boat swung around. Finally, when the two mouths were placed vertically the boat remained immovable. All the evolutions were easy, even without the help of the rudder, and the ways in which the propelling tubes could be placed were capable of being varied _ad infinitum_ by a system of levers.

The Seraing No. 2 had an engine of a nominal power of 40 horses, and took on an average 30 minutes to make the trip, backward and forward, of 85 kilometers, with four stoppages.

The success obtained was perfect, and the running was most satisfactory. It was remarked, only, that from the standpoint of effective duty it would have been desirable to reduce the velocity of the water at its exit from the propellers.

Mr. Poillon attributes the small effective performance to the system employed for putting the water in motion. At time of Mr. Seraing's experiments, only centrifugal force pumps were known, and the theoretic effective duty of these, whatever be the peculiar system of construction, cannot exceed 66 per cent., and, in practice, falls to 40 or 50 per cent. in the majority of cases.

It is probable, then, that in making use of those new rotary pumps where effective duty reaches and often exceeds 80 per cent., we might obtain much better results, and it is this that justifies the new researches that have been undertaken by Messrs. Maginot & Pinette, whose first experiments we are about to make known.

In order to have it understood what interest attaches to these researches, let us state the principal advantages that this mode of propulsion will have over the helix and paddle wheel: The width of side-wheel boats will be reduced by from 20 to 30 per cent., and the draught of water will be diminished in screw steamers to that of the hull itself; the maneuver in which the power of the engine might be directly employed will be simplified; a machine will be had of a sensibly constant speed, and without change in its running; the production of waves capable of injuring the banks of canals will be avoided; the propeller will be capable of being utilized as a bilge pump; all vibration will be suppressed; the boat will be able to run at any speed under good conditions, while the helix works well only when the speed of the vessel corresponds to its pitch; it will be possible to put the propelling apparatus under water; and, finally, it will be possible to run the pump directly by the shaft of the high speed engine, without intermediate gearing, which is something that would prove a very great advantage in the case of electric pleasure boats actuated by piles and accumulators and dynamo-electric machines.

We now arrive at Messrs. Maginot & Pinette's system, the description of which will be greatly facilitated by the diagram that accompanies this article. The inventors have employed a boat 14 meters in length by 1.8 m. in width, and 65 centimeters draught behind and 32 in front. The section of the midship beam is 70 square decimeters, and that of the exhaust port is 4. At a speed of 2.2 meters per second the tractive stress, K, is from 10 to 11 kilogrammes. At a speed of 13.5 kilometers per hour, or 3.75 meters per second, the engine develops a power of 12 horses. The piston is 19 centimeters in diameter, and has a stroke of 15 centimeters. The shaft, in common, of the pump and engine makes 410 revolutions per minute. It will be seen from the figure that suction occurs at the lower part of the hull, at A, and that the water is forced out at B, to impel the vessel forward. C and C' are the tubes for putting the vessel about, and DD' the tubes for causing her to run backward. Owing to the tubes, C, C', the rudder has but small dimensions and is only used for _directing_ the boat. The vessel may be turned about _in situ_ by opening one of the receiving tubes, according to the side toward which it is desired to turn.

This boat is as yet only in an experimental state, and the first trials of her that have recently been made upon the Saône have shown the necessity of certain modifications that the inventors are now at work upon.--_La Nature_.

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A NEW FORM OF FLEXIBLE BAND DYNAMOMETER.

[Footnote: Read before Section G of British Association.]

By Professor W.C. UNWIN.

In the ordinary strap dynamometer a flexible band, sometimes carrying segments of wood blocks, is hung over a pulley rotated by the motor, the power of which is to be measured. If the pulley turns with left-handed rotation, the friction would carry the strap toward the left, unless the weight, Q, were greater than P. If the belt does not slip in either direction when the pulley rotates under it, then Q-P exactly measures the friction on the surface of the pulley; and V being the surface velocity of the pulley (Q-P)V, is exactly the work consumed by the dynamometer. But the work consumed in friction can be expressed in another way. Putting [theta] for the arc embraced by the belt, and [mu] for the coefficient of friction,

Q/P = [epsilon]^{[mu]^{[theta]}},

or for a given arc of contact Q = [kappa]P, where [kappa] depends only on the coefficient of friction, increasing as [mu] increases, and _vice versa_. Hence, for the belt to remain at rest with two fixed weights, Q and P, it is necessary that the coefficient of friction should be exactly constant. But this constancy cannot be obtained. The coefficient of friction varies with the condition of lubrication of the surface of the pulley, which alters during the running and with every change in the velocity and temperature of the rubbing surfaces. Consequently, in a dynamometer in this simple form more or less violent oscillations of the weights are set up, which cannot be directly controlled without impairing the accuracy of the dynamometer. Professors Ayrton and Perry have recently used a modification of this dynamometer, in which the part of the cord nearest to P is larger and rougher than the part nearest to Q. The effect of this is that when the coefficients of friction increase, Q rises a little, and diminishes the amount of the rougher cord in contact, and _vice versa_. Thus reducing the friction, notwithstanding the increase of the coefficient. This is very ingenious, and the only objection to it, if it is an objection, is that only a purely empirical adjustment of the friction can be obtained, and that the range of the adjustment cannot be very great. If in place of one of the weights we use a spring balance, as in Figs. 2 and 3, we get a dynamometer which automatically adjusts itself to changes in the coefficient of friction.

For any increase in the coefficient, the spring in Fig. 2 lengthens, Q increases, and the frictional resistance on the surface of the pulley increases, both in consequence of the increase of Q, which increases the pressure on the pulley, and of the increase of the coefficient of friction. Similarly for any increase of the coefficient of friction, the spring in Fig. 3 shortens, P diminishes, and the friction on the surface of the pulley diminishes so far as the diminution of P diminishes the normal pressure, but on the whole increases in consequence of the increase of the coefficient of friction. The value of the friction on the surface of the pulley, however, is more constant for a given variation of the frictional coefficient in Fig. 3 than in Fig. 2, and the variation of the difference of tensions to be measured is less. Fig. 3, therefore, is the better form.

A numerical calculation here may be useful. Supposing the break set to a given difference of tension, Q-P, and that in consequence of any cause the coefficient of friction increases 20 per cent., the difference of tensions for an ordinary value of the coefficient of friction would increase from 1.5 P to 2 P in Fig. 2, and from 1.5 P to 1.67 P in Fig. 3. That is, the vibration of the spring, and the possible error of measurement of the difference of tension would be much greater in Fig. 2 than in Fig. 3. It has recently occurred to the author that a further change in the dynamometer would make the friction on the pulley still more independent of changes in the coefficient of friction, and consequently the measurement of the work absorbed still more accurate. Suppose the cord taken twice over a pulley fixed on the shaft driven by the motor and round a fixed pulley, C.

For clearness, the pulleys, A B, are shown of different sizes, but they are more conveniently of the same size. Further, let the spring balance be at the free end of the cord toward which the pulley runs. Then it will be found that a variation of 20 per cent. in the friction produces a somewhat greater variation of P than in Fig. 3. But P is now so much smaller than before that Q-P is much less affected by any error in the estimate of P. An alteration of 20 per cent. in the friction will only alter the quantity Q-P from 5.25 P to 5.55 P, or an alteration of less than 6 per cent.

To put it in another way, the errors in the use of dynamometer are due to the vibration of the spring which measures P, and are caused by variations of the coefficient of friction of the dynamometer. By making P very much smaller than in the usual form of the dynamometer, any errors in determining it have much less influence on the measurement of the work absorbed. We may go further. The cord may be taken over four pulleys; in that case a variation of 20 per cent. in the frictional coefficient only alters the total friction on the pulleys 1¼ percent. P is now so insignificant compared with Q that an error in determining it is of comparatively little consequence.

The dynamometer is now more powerful in absorbing work than in the form Fig. 3. As to the practical construction of the brake, the author thinks that simple wires for the flexible bands, lying in V grooves in the pulleys, of no great acuteness, would give the greatest resistance with the least variation of the coefficient of friction; the heat developed being in that case neutralized by a jet of water on the pulley. It would be quite possible with a pulley of say 3 feet diameter, and running at 50 feet of surface velocity per second, to have a sufficiently flexible wire, capable of carrying 100 lb. as the greater load, Q. Now with these proportions a brake of the form in Fig. 3 would, with a probable value of the coefficient of friction, absorb 6 horse power. With a brake in the form Fig. 4, 8.2 horse power would be absorbed; and with a brake in the form Fig. 5, 8.8 horse power would be absorbed. But since it would be easy to have two, three, or more wires side by side, each carrying its load of 100 lb., large amounts of horsepower could be conveniently absorbed and measured.

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SEE'S GAS STOVE.

This stove consists of two or more superposed pipes provided with radiators. A gas burner is placed at the entrance of either the upper or lower pipe, according to circumstances. The products of combustion are discharged through a pipe of small diameter, which may be readily inserted into an already existing chimney or be hidden behind the wainscoting. The heat furnished by the gas flame is so well absorbed by radiation from the radiator rings that the gases, on making their exit, have no longer a temperature of more than from 35 to 40 degrees.

The apparatus, which is simple, compact, and cheap, is surrounded on all sides with an ornamented sheet iron casing. Being entirely of cast iron, it will last for a long time. The joints, being of asbestos, are absolutely tight, so as to prevent the escape of bad odors. The water due to the condensation of the gases is led through a small pipe out of doors or into a vessel from whence it may evaporate anew, so as not to change the hygrometric state of the air. The consumption of gas is very small, it taking but 250 liters per hour to heat a room of 80 cubic meters to a temperature of 18° C.--_Revue Industrielle_.

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The number of persons killed by wild animals and snakes in India last year was 22,125, against 21,427 in the previous year, and of cattle, 46,707, against 44,669. Of the human beings destroyed, 2,606 were killed by wild animals, and 19,519 by snakes. Of the deaths occasioned by the attacks of wild animals, 895 were caused by tigers, 278 by wolves, 207 by leopards, 356 by jackals, and 202 by alligators; 18,591 wild animals and 322,421 snakes were destroyed, for which the Government paid rewards amounting to 141,653 rupees.

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RECTIFICATION OF ALCOHOL BY ELECTRICITY.

Some time ago, Mr. Laurent Naudin, it will be remembered,[1] devised a method of converting the aldehydes that give a bad taste and odor to impure spirits, into alcohol, through electrolytic hydrogen, the apparatus first employed being a zinc-copper couple, and afterward electrolyzers with platinum plates.

[Footnote 1: See SCIENTIFIC AMERICAN SUPPLEMENT of July 29, 1882, p. 5472.]

His apparatus had been in operation for several months, in the distillery of Mr. Boulet, at Bapeaume-les-Rouen, when a fire in December, 1881, completely destroyed that establishment. In reconstructing his apparatus, Mr. Naudin has availed himself of the experience already acquired, and has necessarily had to introduce important modifications and simplifications into the process. In the zinc-copper couple, he had in the very first place proposed to employ zinc in the form of clippings; but the metal in this state presents grave inconveniences, since the subsidence of the lower part, under the influence of the zinc's weight, soon proves an obstacle to the free circulation of the liquids, and, besides this, the cleaning presents insurmountable difficulties. This is why he substituted for the clippings zinc in straight and corrugated plates such as may be easily found in commerce. The management and cleaning of the pile thus became very simple.

The apparatus that contains the zinc-copper couple now has the form shown in Fig. 1. It may be cylindrical, as here represented, or, what is better, rectangular, because of the square form under which the sheets of zinc are found in commerce.

In this vessel of wood or iron plate, P, the corrugated zinc plates, b, b', b", are placed one above the other, each alternating with a flat one, a, a', a". These plates have previously been scoured, first with a weak solution of caustic soda in order to remove every trace of fatty matter derived from rolling, and then with very dilute hydrochloric acid, and finally are washed with common water. In order to facilitate the disengagement of hydrogen during the reaction, care must be taken to form apertures in the zinc plates, and to incline the first lower row with respect to the bottom of the vessel. A cubical pile of 150 hectoliters contains 105 rows of No. 16 flat and corrugated zinc plates, whose total weight is 6,200 kilogrammes. We obtain thus a hydrogenizing surface of 1,800 square meters, or 12 square meters per hectoliter of impure spirits of 50° to 60° Gay-Lussac. The raw impure spirits enter the apparatus through the upper pipe, E, and, after a sufficient stay therein, are drawn off through the lower pipe, H, into a reservoir, R, from whence, by means of a pump, they are forced to the rectifier.

The hydrogen engendered during the electrolysis is disengaged through an aperture in the cover of the pile.

As a measure of precaution, the hydrogen saturated with alcoholic vapors may be forced to traverse a small, cooled room. The liquefied alcohol returns to the pile. At a mean temperature of 15°, the quantity of alcohol carried along mechanically is insignificant. In order to secure a uniformity of action in all parts of the spirits, during the period devoted to the operation, the liquid is made to circulate from top to bottom by means of a pump, O. The tube, N, indicates the level of the liquid in the vessel. The zinc having been arranged, the first operation consists in forming the couple. This is done by introducing into the pile, by means of the pump, O, a solution of sulphate of copper so as to completely fill it.

The adherence of the copper to the zinc is essential to a proper working of the couple, and may be obtained by observing the following conditions:

1. Impure spirits of 40° Gay-Lussac, and not water, should be used as a menstruum for the salt of copper.

2. The sulphatization should be operated by five successive solutions of ½ per cent., representing 20 kilogrammes of sulphate of copper per 100 square meters of zinc exposed, or a total of 360 kilogrammes of sulphate for a pile of 150 hectoliters capacity.

3. A temperature of 25° should not be exceeded during the sulphatization.

The use of spirits is justified by the fact that the presence of the alcohol notably retards the precipitation of copper. As each charging with copper takes twenty-four hours, it requires five days to form the pile. At the end of this time the deposit should be of a chocolate-brown and sufficiently adherent; but the adherence becomes much greater after a fortnight's operation.

Temperature has a marked influence upon the rapidity and continuity of the reaction. Below +5° the couple no longer works, and above +35° the reaction becomes vigorous and destroys the adherence of the copper to such a degree that it becomes necessary to sulphatize the pile anew. The battery is kept up by adding every eight days a few thousandths of hydrochloric acid to a vatful of the spirits under treatment, say 5 kilos. of acid to 150 hectoliters of spirits. The object of adding this acid is to dissolve the hydrate of oxide of zinc formed during the electrolysis and deposited in a whitish stratum upon the surface of the copper. The pile required no attention, and it is capable of operating from 18 months to two years without being renewed or cleaned.

Passing them over, the zinc-copper couple does not suffice to deodorize the impure spirits, so they must be sent directly to a rectifier. But, in certain cases, it is necessary to follow up the treatment by the pile with another one by electrolysis. The voltameters in which this second operation is performed have likewise been modified. They consist now (Fig. 2) of cylindrical glass vessels, AH, 125 mm. in diameter by 600 in height, with polished edges. These are hermetically closed by an ebonite cover through which pass the tubes, B' C' and B C, that allow the liquid, E+E-E'+E', to circulate.

The current of spirits is regulated at the entrance by the cock, R, which, through its division plate, gives the exact discharge per hour. In addition, in order to secure great regularity in the flow, there is placed between the voltameters and the reservoir that supplies them a second and constant level reservoir regulated by an automatic cock.

In practice, Mr. Naudin employs 12 voltameters that discharge 12 hectoliters per hour, for a distillery that handles 300 hectoliters of impure spirits every 24 hours. The electric current is furnished to the voltameters by a Siemens machine (Fig. 3) having inductors in derivation, the intensity being regulated by the aid of resistance wires interposed in the circuit of the inductors.

The current is made to pass into the series of voltameters by means of a commutator, and its intensity is shown by a Deprez galvanometer. The voltameters, as shown in the diagram, are mounted in derivation in groups of two in tension. The spirits traverse them in two parallel currents. The Siemens machine is of the type SD2, and revolves at the rate of 1,200 times per minute, absorbing a motive power of four horses.

The disacidification, before entering the rectifier, is effected by the metallic zinc. Let us now examine what economic advantages this process presents over the old method of rectifying by pure and simple distillation. The following are the data given by Mr. Naudin:

In ordinary processes (1) a given quantity of impure alcohol must undergo five rectifications in order that the products composing the mixture (pure alcohol, oils, etc.) may be separated and sold according to their respective quality; (2) the mean yield in the first distillation does not exceed 60 cent.; (3) the loss experienced in distillation amounts, for each rectification, to 4 per cent.; (4) the quantity of essential oils (mixture of the homologues of ethylic alcohol) collected at the end of the first distillation equals, on an average, 3.5 per cent.; (5) the cost of a rectification may be estimated at, on an average, 4 francs per hectoliter.

All things being equal, the yield in the first operation by the electric method is 80 per cent., and the treatment costs, on an average, 0.40 franc per hectoliter. The economy that is realized is therefore considerable. For an establishment in which 150 hectoliters of 100° alcohol are treated per day this saving becomes evident, amounting, as it does, to 373 francs.

We may add that the electric process permits of rectifying spirits which, up to the present, could not be rectified by the ordinary processes. Mr. Naudin's experiments have shown, for example, that artichoke spirits, which could not be utilized by the old processes, give through hydrogenation an alcohol equal to that derived from Indian corn.--_La Nature_.

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PLASTIC CARBON FOR BATTERIES.

Max Nitsche-Niesky recommends the following in _Neueste Erfindung_.: Good coke is ground and mixed with coal-tar to a stiff dough and pressed into moulds made of iron and brass. After drying for a few days in a closed place, it is heated in a furnace where it is protected from the direct flames and burned, feebly at first, then strongly, the fire being gradually raised to white heat which is maintained for 6 or 8 hours. The fire is then permitted to slowly go down, and when perfectly cold the carbon is taken out of the furnace.

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