THE ARTIFICIAL HAND-BY SIR GEORGE CAYLEY, BART. case it is desirable to give this substitute all the efficient movements it is capable of. With this view, let the thumb piece, as at A, fig. 5, be furnished with a horizontal joint capable of being screwed firmly against a spring plate, so as to 199 create sufficient friction to prevent its turning with inconvenient freedom, (any required position may also be secured by a spring catch) By means of this joint the thumb can at any time be turned, as in the natural hand, out of the way of Fig. 5. the grasp of the fingers, so that these may close round till they meet the ball of the thumb. This will enable many things to be held more conveniently and firmly than when the thumb meets the extended fingers at some intermediate point, and stops their further progress. To effect this greater range of the joints of the fingers, some little adjustment of the former plan is required. It may be effected many ways, but let the arrangement shown at B, fig. 5, suffice for the present to explain what is intended. And these movements being chiefly similar to those in fig. 4, (marked so in the plate by mistake,) will readily be understood, without further explanation, by reference to that figure. George Douseland can write, though with difficulty, with the hand as constructed in fig. 2, but an inventive young friend of mine has suggested the use of a spring movement in the last joint of the thumb, as at C, fig. 5, which will enable the pen to obey the pressure of the fingers backward in the down strokes and to propel it forward in the up ones, as the fingers relax their force. This light elasticity of the thumb ceases when pressed back to its natural position by the joint being made incapable of receding further; and, hence, it will be no detriment to the firm grasp between it and the fingers. To avoid confusion in the figures they are drawn so as to show the movement of one finger only; and in the hand worn by George Douseland there is but one such movement, all the cork fingers being united side by side, and fixed to one broad thin steel plate, jointed, as shown in fig. 2, and covered with continuous leather, only stitched down to mark the distinction of the fingers under it. For common use in most cases this will be sufficient; but where a more expensive apparatus can be afforded, and the appearance of having a real hand is an object, this thin steel plate can be separated into digits, though united at the base as the human hand, and jointed at the proper places in due proportion to each finger; and the tendons piercing these plates, may be either hinged to fixed joints, as at S, fig. 2, or worked from a horizontal extension of the joint H, fig. 4. All the required movements 200 FENN'S SPRING ADJUSTING PLANE. can be effected by catgut or other tendons attached to the joints of the fingers, as in the natural hand, and terminating in loops or eyes, on different parts of such a hinged bar as F H, fig. 4, so as to give them different ranges of tension to suit their respective purposes. This structure implies the necessity of a counteracting worm, or other spring movement, to extend the fingers and thumb again. Very light and elegant hands may be made on this plan, which would be suitable for the fair sex, and for light work. I before said, the first drawing made of the hand for George Douseland was on this plan; but I found that he could lift the weight of five stone with the stump, and that the strength, precision, and durability of steel joints and tendons was more suitable to his work. These have also the great advantage of giving both extension and contraction, with no counteracting spring to weaken the effect. By one simple, lasting, and efficient means, both these actions are effected with perfect precision in all weathers. This instrument, in all its forms, has only been represented as working when the spring bolt L, fig. 1, secured the lower arm from turning on the hinge F; but conceive this spring bolt occasionally drawn back, and secured from acting; and that a spring friction plate held the joint F, from turning, with less than three stone weight applied at the ring D by the stump, the grasp of the hand could then be used only up to that extent of pressure, sufficient, say, for example, to lift a can full of liquid; thus, if more than three stone force be applied, the friction of the joint will be overcome, the can will still be retained with the same power, but the movement of the joint will allow it to be lifted to the mouth. This is only one example of a very important principle, applicable to innumerable instances, and which greatly increases the use of the apparatus. (To be continued.) LIGHTING BY ELECTRICITY. Mr. Weekes's plan for lighting towns by electricity, which first appeared in the Mechanics' Magazine, as far back as June, 1831, and has been since fully developed by him in an article in the Electrical Magazine for January last, republished in this Journal of the 12th January, has been lately reinvented in America, by two persons in Cincinnati, of the names of Mills and Saunders. We extract the following notice of a successful experiment made by them from the Cincinnati Mechanic : "The apparatus with which the light is made is small, to allow of easy transportation. But it may be increased to an indefinite extent, and with its enlargement is the increase of the size of the light. From our own observation we should suppose the power of the light could not be increased. We never could conceive a light more brilliant. Though but the size of a pea, it is sufficient to illuminate quite a large room, and forbids the steady glance of the eye. The blaze of a candle 20 feet distant from the apparatus, and 3 feet from the wall, cast upon the wall a thick shadow-so much more brilliant is 'the light,' though not one-twentieth the size of the candle's flame. What will be the power of this light when increased to the size of a gaslight? We cannot conceive. The apparatus is not costly; and for lighting Cincinnati, two towers will be considered sufficient to illuminate the whole city, and at a very small expense." FENN'S SPRING ADJUSTING PLANE. [Registered under the Act for Protection of Articles of Utility. Joseph Fenn, of Newgate-street, toolmaker, Proprietor.] We have here another valuable addition to the list of mechanical tools, from the eminent workshop of Fenn, of Newgate-street. Fig. 1, of the prefixed engravings, is a side elevation of this improved plane, partly in section. A is a bed plate for the cutting iron D; Ba screwed rod fixed at the back of this bed plate, being passed through bearings a a, projecting from the bed plate at top and bottom. C is a traversing nut which works on the shank of the rod B, and has an oblong pin b, which protrudes from it into and through a groove which runs down the centre of the bed plate. The cutting iron D is attached to the bed plate by means of the pin b, which fits into a corresponding hole in the top of the iron; and as this pin is raised or lowered, by the turning of the screwed rod to the right or left, it raises or lowers the iron. E is the cover of the cutting iron; F is a spring holder, a plan of which is given separately in fig. 2; f is the handle of this holder, and g the spring at the back; h1 is the 202 ON WARMING AND VENTILATING BUILDINGS, ETC. tion is more easily effected in cold than direction, unless the atmosphere be very warm, and then only for a short time. In support of the doctrine of the diffusion of gases, great importance is attached to Graham's bottle experiment, but which, with all deference to that great experimentalist, I consider as no proof whatever, in consequence of the pressure of the atmosphere, on which specific gravity depends, being entirely cut off. If the smallest possible hole were made in the bottom of the two bottles, it is unquestionable that the hydrogen would ascend, and the carbonic acid descend, however intimately these two gases might be mixed. If a bladder be filled with an admixture of hydrogen and carbonic-acid gas, it is well known that the whole of the hydrogen will fly off and leave the other gas behind, and if either of these gases be passed into a vessel, agreeably to their specific gravities, the whole of the air previously in the vessel will be driven out, and the gas will occupy the entire space; how is it, then, I ask, that the law of diffusion does not in the one case prevent the escape of the hydrogen, and in the other cause an admixture of the hydrogen or carbonic acid with the air in the vessel ? In fact, Graham's own experiment of the tube with a plaster cap explains the cause—at all events, so far as the hydrogen is concerned. Even supposing the present theory to be correct, the propriety of adopting it becomes very questionable. All medical men are agreed in the propriety of keeping the feet warm and the head cool, whereas, the cold air introduced at the bottom of the apartment, cannot by any possibility ascend until it shall have robbed the lower extremities of the body of sufficient heat to raise its temperature above that of the external air, so that, whilst the feet and legs are constantly as cold as if they were surrounded with ice, the air never reaches the lungs but in a heated vitiated state, which is, I believe, immediately the reverse of what should be. That great difficulty will be at all times experienced, in maintaining the purity of the atmosphere of a crowded room by spontaneous ventilation, must be admitted, but it appears to me, that if the air were admitted into the room, in such manner as in no way to impede the motions of the gases, as they escape from the lungs, agreeably to their specific gravities, much ON WARMING AND VENTILATING BUILDINGS, ETC. benefit would be derived therefrom, and in fact, practice shows that this is the best possible system of ventilation; for when the temperature of the atmosphere is low, and the condensation of the vapour and carbonic-acid pretty rapid, the cold air not rising sufficiently fast to supply the partial vacuum, there is a constant rush of air downwards, and so great is this descent from the cupola of the theatre of the London Mechanics' Institution, that it became absolutely necessary on the 5th of February to remove the line to which I suspended my bottle, to allow of the windows being entirely closed. When, however, I commenced this correspondence, (No. 1098, Aug. 24, 1844,) it was not with the view of at present agitating the question of spontaneous ventilation, but to introduce, as I conceived, a cheap and efficacious means of warming and ventilating apartments, particularly offices, at that time of the year, when, from the temperature of the external atmosphere, cold air cannot be admitted into the room, and that I am not altogether singular in preferring the downward to the upward current, I may remark, that on reference to the last number of the Royal Engineer Papers, it will be seen that Major Jebb, the Inspector General of Military Prisons, introduces the pure warm air at the top of the cell, and draws off the foul air at the bottom, and the same method is followed by Messrs. Haden, of Trowbridge, a plan they have doubtless adopted for the obvious reason, that man's respiratory organs are turned downwards, and were not intended by nature as receptacles for dust. But by respiration, atmospheric air, a compound of one of oxygen to four of nitrogen, is taken into the lungs, and oxygen, nitrogen, and carbonic-acid gas are expelled, and as carbonic-acid gas occupies the same space as the oxygen consumed, it is quite clear, that for every volume of carbonicacid gas generated, four volumes of nitrogen must also be liberated into the room, supposing none of it to be consumed, and as this gas is as fatal to respiration as carbonic-acid gas, unless it be also got rid of, the ventilation must be very imperfect. It is also a question of vital importance, and which has yet to be decided, whether any and what portion of the nitrogen of the air is consumed during the process of respiration. Liebig as 203 serts, and his assertion has gone the round of the philosophical press, that a portion of the oxygen of the air taken into the lungs during respiration combines with the hydrogen of the food and forms the vapour given off by perspiration. Whatever might be my Own opinion on this question, (for after all this can be but matter of opinion,) I should be doubtful of its correctness when opposed to that of such a man as Liebig; and I should hesitate in now agitating the question, were it not that this great philosopher had long since proved that such a process as this is at variance with the provisions and wisdom of nature. He has shown that ammonia is essential to vegetation; and nature, we know, never creates a necessity without providing for it. And to what source are we to trace the production of ammonia but to the hydrogen of organic matter? That hydrogen has a greater affinity for oxygen than any other substance under the influence of combustion or the electric spark, there cannot be a question; but unless I am most egregiously deceived, hydrogen never does combine with oxygen to form vapour under the influence of negative electricity. Some years since, I made many experiments on the decomposition of organic matter, particularly animal, in order to determine what action air had on it during the process of putrefaction. For this purpose, I made use of a copper still, to the feeder of which I connected a pipe that went to the bottom of the still, and to the top of the still I connected a stop-cock. Having partly filled the still with human secretions, (mixed with water) which I' had previously washed with dilute hydrochloric acid to deprive them of all the ammonia, I luted on the top, and left the still quiet for two or three days for the process to go on. I found as a general result that putrefaction was more rapid when the vessel was in connection with the earth than if insulated; and that the process was still more rapid if the still were immersed in the earth. The gases which I drew off at first consisted principally of sulphuretted hydrogen and carburetted hydrogen and the components of the air. And after the process had gone on for some time ammonia and carbonic acid were amongst the gaseous compounds in abundant pro |