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 minate the whole city, and at a very small expense." illu 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 addi tion 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 ON WARMING AND VENTILATING BUILDINGS-FERMENTATION THEORY OF RAIN AND OF ARTIFICIAL LIGHT. Sir,-In my last letter (No. 1106, of Oct. 19, 1844,) on the subject of ventilation, &c. I stated m intention of putting to the AND PUTREFACTION BY FRANKLIN COXWORTHY, ESQ., test of experiment the present theory of the diffusion of gases, as having reference to the opinion that spontaneous ventila 202 ON WARMING AND VENTILATING BUILDINGS, ETC. tion is more easily effected in cold than in warm weather, on the principle that the difference of weight in the exterior and interior columns of air increased with the difference of temperature in the interior and exterior of the building, and I think that any result more conclusive on the subject could not possibly be adduced. I have found, as a general result, that when the atmosphere was about the temperature of 50°, the amount of carbonic-acid gas, appreciable in the pit of the theatre of the London Mechanics' Institution, and in the cupola, was about much the same, having obtained a precipitate of 11 or 12 grains of carbonate of baryta to 3,000 cubic inches of air passed through my bottle, it being observed, however, that in the cupola the products of respiration of the whole house were concentrated in the cupola, which was not the case in the pit; and that the amount of precipitate obtained in the cupola increased with the increase of temperature, and decreased as the weather became more cold. But the most remarkable result I obtained, and which certainly by far exceeded my expectation, was on the 13th of December, immediately behind the upper gallery of Drury Lane Theatre, when the pit was quite full, and the remainder of the house about half full; here I passed the same quantity of air through my bottle, and obtained not even an appreciable amount of precipitate. The weather on this occasion was intensely cold. It is clear then, that, so far as the carbonic-acid gas is concerned, the cause of ventilation being effected so readily during cold weather is in no way referable to the difference of weight in the interior and exterior columns, but is solely attributable to the existence of the beautiful provision of nature to which I referred in my letter (No. 1102 of Sept. 21, 1844). For proof that vapour, when charged with carbonicacid gas, undergoes condensation when exposed to a cold atmosphere, I need only refer, to the steam as it issues from the funnel of a locomotive engine. On the Greenwich line I have invariably observed that the steam no sooner quits the funnel than it immediately descends over the parapet of the line, and continues descending until it reaches the earth. Now here the temperature of the vapour is infinitely above that of the lungs, and still it never has an upward 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 venNTILATING 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 204 ON WARMING AND VENTILATING BUILDINGS, ETC. portions, and with these latter bodies the water in the still was highly charged as well as with sulphuretted hydrogen. About the same time that I was engaged in these experiments a cesspit was emptied in the yard adjoining to my own, and the weather being then very hot and what is termed sultry, the stench that arose from it became unbearable. With a view to get rid of the nuisance, as well as to form some idea of the amount of the hydrogen compounds that were being generated, I mixed together the proper proportions of manganese and salt in an old jug and placed on the top of the mixture a cup full of dilute sulphuric acid. And when I had lowered the jug to the bottom of the pit, I upset the acid by pulling a string previously attached to the handle of the cup. I had no sooner done this than the whole yard became filled to the second floor windows with a dense white smoke, which continued issuing ftom the pit for at least fifteen or twenty minutes in large volumes, and was still perceptible the next day. Now if the hydrogen of matter under the influence of putrefaction, or a negative state of electricity, possessed the same affinity for oxygen that it has during combustion or the formation of chlorine by the decomposition of hydrochloric acid, it is quite clear that none of these compounds could be formed, as the whole of the hydrogen would be converted into vapour; and it is equally evident that as the source from which the animal kingdom derives its food contains no ammonia and but little nitrogen, that the greater part of the nitrogen that enters into the composition of the ammonia, must be obtained from the atmosphere, either during the process of respiration or putrefaction, but more probably both. And I suspect that if Liebig had stated that a portion of the nitrogen taken into the lungs during respiration enters into combination with the hydrogen of our food and forms the ammonia that escapes from our system with respiration, he would have been much nearer the truth than in making the assertion he has. During the decomposition of animal matter there is liberated carbonic-acid gas, ammonia, carburetted, phosphuretted, and sulphuretted hydrogen. Carbonicacid is given off from the lungs of ani mals by respiration; ammonia escapes through the pores of the skin with perspiration, and is contained in great quantities in animal secretions, as well as sulphuretted, carburetted and phosphuretted hydrogen, the decomposition in both cases taking place under the influence of negative electricity. In the July Number, of 1840, of Dr. Silliman's Journal, is published a most interesting account illustrative of the vast quantity of carburetted hydrogen that is generated during the decomposition of vegetable matter in water. After describing the circumstances that induced the writer of the article to collect and burn some gas that escaped from a pond in which the students of West Town boarding school, Chester Co., Penn., were in the habit of bathing, he observes that he was induced to get the boys to bathe in the evening, and told them that he was going to set the pond afire, and that "the usual preparation for bathing being made, some fifty of the less timid entered the water with the injunction to step as lightly as possible till the pond was discovered to be on fire, when all would be at liberty to proceed as would best suit their inclinations. We soon came to a favourable spot, and the gas beginning to come up pretty freely a lighted taper was brought near the surface, when in an instant a lambent flame played upon our unprotected bodies, and cast a gloomy light upon the surrounding forest, disclosing here and there, amid the thick underbrush, the pale faces of their shouting companions who remained upon the bank. In the hurry, the injunction to step lightly was forgotten, and the general stir of the leaves which took place extricated the gas in such abundance that the flame rose several feet above our heads. As they separated from me I raised my feet from the bottom, and found it much more difficult to suppress my laughter than to extinguish the flames." M. Boussingault, in a very elaborate paper read before the Academy of Sciences on the 4th of August, 1834, details a great number of experiments which he made within the tropics in order to determine the presence of malaria (miasma) in the atmosphere, and gives as a general result of his labours that one part of air contains, taking an average |