behind, as will be readily admitted when I state, that one part by weight of explosive cotton prepared by my method, is equal in its destructive effects to seven parts of gunpowder, if applied to rifles, guns, or in blasting rocks. My method is as follows: Mix together three parts (by volume) of nitric acid of 52° Beaumé, and rather less than two parts sulphuric acid of 72° Beaumé, and the compound acid will become a little heated. Wait till it becomes cool; then take a portion of well-dried and cleansed cotton; lay it for only two or three minutes in the compound acid, and take care that every part of the cotton comes in contact with the acid. Next remove the acid by means of a press, and wash the cotton with cold water till nothing of the acid is perceptible, after which the water is to be removed, and the cotton well dried. The "explosive cotton" is then in a finished state. Explosive cotton prepared by this very simple and cheap method, has all the properties praised in M. Schonbein's invention, and seven times the force of gunpowder. Paper, sawdust, flax, calico, &c., if prepared in the same way, are also rendered explosive; but cotton answers best, because of its division into such a multitude of minute filaments. I shall be very anxious to hear whether M. Schonbein's method and the above described be not one and the same. I am, Sir, yours, &c, EMIL WEEGER. Brunn, (Austria,) Nov. 26, 1846. REMARKS ON THE ALLEGED IDENTITY OF THE GUN-COTTON WITH XYLOIDINE, AND ITS PRACTICAL VALUE AS COMPARED WITH GUNPOWDER. Sir, I have read the letter of Professor Schonbein, pointing out that his guncotton is a distinct invention from the xyloidine of Braconnot; for that the xyloidine was, according to Braconnot's own statement, converted by acetic acid into a sort of varnish, whereas acetic acid did not, either with or without heat, produce any effect on his (Professor Schonbein's) gun-cotton. What that gun-cotton is, we shall all in due time learn; meanwhile, it seems to me pretty clear, that cotton prepared with nitric acid only, or with a mixture of nitric and sulphuric acid, is identical with Professor Schonbein's, although he may, very probably, have some peculiar and better plan for mixing the acids and preparing the cotton than has been generally adopted by experimentalists. I would also remark, that cotton prepared as above may be treated with acetic acid, either with or without heat, without losing any of its power. This I have myself tried, and it seems to confirm my view of such cotton being identical with that of Professor Schonbein. I have not myself been able to refer to the volume of the Comptes Rendus, containing M. Braconnot's account of his discovery; but, if the extracts I have seen are correct, it seems to me that the substance he termed xyloidine was starch dissolved in nitric acid, and then precipitated, &c.; and that he went on to remark, that, without dissolving the cellulose, paper, tow, or cotton might be simply saturated with nitric acid, and would produce an equally explosive substance. But it does not seem clear to me, from the extracts I have seen, that he meant to include all these substances under the name of xyloidine, though he probably did so; nor could he have meant to state that paper, tow, or cotton, so prepared, would dissolve into a varnish in acetic acid; for they will not do so, though I think it very probable that starch, as he prepared it, would. I have not, however, tried it myself, I may here remark, that it was asserted in some of the earlier notices on the subject, that tow would not succeed as a substitute for cotton. This is not, however, the case; and though tow leaves a slight residuum, it might, in some cases, be preferable from its cheapness, were this new explosive to be generally adopted. But I do not myself see how this can be done with economy. Coarse powder is worth about 5d. per lb., whereas common cotton cannot be reckoned at less than 6d. per lb.; and the expense of the acids would be at least three times as great, probably much more, for every lb. of this new explosive-especially as I have invariably found the perfect success of the preparation to depend not upon merely saturating, but actually flooding the cotton with the acids. This makes washing it clear of the acids an easy matter, and also prevents all tendency to cake or knot, which will otherwise be found very troublesome. REMARKS ON THE IDENTITY OF THE GUN-COTTON WITH XYLOIDINE. I cannot agree with the remarks contained in Mr. Greener's article, as to the danger to be apprehended from the facility with which every chemist's boy may manufacture this new explosive. There was no great difficulty to prevent their making gunpowder: indeed I have myself known coarse gunpowder manufactured by a schoolboy of ten years old. Nor do I agree in thinking that it would be inapplicable for projectiles, from the danger of bursting the gun, attendant on its very rapid ignition. The momentum acquired by a ball fired from a gun with powder, may be considered due to one chief impulse, succeeded by a series of increments of force, some of the powder continuing to burn till the ball leaves the gun, and some being blown out, still unburned, together with the ball; whereas the momentum acquired by a ball fired from a gun with gun-cotton, may be considered due to one single impulse. But, after all, any evil effects of this instantaneous explosion might be guarded against by making guns heavier and stronger about the chamber; and an equal range might be obtained with a far shorter barrel than at present. The shot would not, perhaps, be so well kept together, nor would so good an aim be afforded by such a barrel. For many mining purposes, this very instantaneousness of explosion, and also the absence of all offensive smoke, must render guncotton invaluable: for others, (as where it is desired to heave up large beds of rock, without bursting them into fragments,) powder would be preferable. The low temperature at which it explodes seems much more conclusive against its use for the purposes of heavy artillery. Gunpowder requires a temperature of 600° Fah. to explode it; nevertheless, in spite of sponging, guns with rapid firing become so heated as to render the loading them unsafe-à fortiori, it would be unsafe with gun-cotton, which explodes at one-third of the abovenamed temperature. In conclusion, I would remark one peculiarity of the gun-cotton, which I have not yet seen adverted to. From its spongy texture, the least pressure ejects the permeating air, and, destroying its quasi granulation, prevents the compressed part from exploding. Thus, if you take a lock of the cotton between your finger and thumb, and hold it to a candle, 569 it will explode only to the point where the pressure of your finger and thumb commences, and no further. This property would prevent its being a substitute for gunpowder; while in the preparation of most fire-works, it would render it available as a manageable motive force, could it be procured at a sufficiently low cost. A pair of fluted cylinders, for instance, (if necessary, hollow, and cooled within by water,) might throw off a cordon of the cotton, the portions of which from time to time thrown off, and uncompressed, would alone take fire; a double-action engine might thus be easily constructed. It should also be remarked, that the rapidity of the explosion of the cotton may also be in great measure regulated by a process analogous to the finer or coarser granulation of gunpowder; guncotton, with its delicate fibres, may be compared to a very finely granulated gunpowder, with air penetrating between every atom. Twist the prepared cotton tightly into threads, small or large, and you obtain a cotton answering to gunpowder of a coarser, or still coarser grain. My subject has carried me far beyond the limits I had proposed to myself, which is the less excusable, as I have neglected to ascertain by reference to the Comptes Rendus of 1833, whether I am correct in the view I have taken of M. Braconnot's account of his xyloidine, &c. I am, Sir, yours, &c., I. C. French Experiments with the Gun-Cotton. The following results of some experiments recently made in Paris by MM. Suzanne and De Mezières, respecting the preparation and balistical properties of the gun-cotton, have been communicated to the French Academy of Sciences. In all these experiments cotton was prepared, (at first not carded, and afterwards carded,) by dip-, ping it into a mixture containing equal parts of concentrated azotic acid and sulphuric acid, and this substance was immediately well washed in water. By this process there were obtained different samples of gun-cotton, by successively varying the duration of the immersion, the quantity and the state of the acids, &c. These samples were subsequently tested with a firearm called the fusil-pendule. 1. Five grammes of gun-cotton produce the same effect upon a muket ball as 13 or 2. But to possess such power, the cotton must be well cleansed, and steeped in a mixture composed of equal parts of azotic and sulphuric acid. 3. The duration of the immersion is unimportant; it may, however, be stated that the best samples had been steeped from 10 to 15 minutes. 4. The cotton must not pass beyond the level of the liquid. 5. The cotton should be dried slowly, and not be subjected, especially when it is still damp, to a temperature exceeding 100 degrees. 6. By washing it in water saturated with saltpetre, its power is a little increased; but it is not thought that this process is worth the additional expense. RECENT AMERICAN PATENTS. [Selected and abridged from Mr. Keller's Reports in the Franklin Journal for October, 1846.] AN IMPROVED METHOD OF COMBINING AND CONNECTING CRANKS AND CRANK PINS OF STEAM ENGINES. Frederick E. Sickels. Claim." What I claim as my invention is connecting a crank pin with two cranks, by means of turning and sliding joints combined, whether the pin be made to slide in both cranks or only in one, so as to equalize the strain of the engine on each crank, and allow them to move and compensate for any error in the relative position of the crank shafts, as herein described." FOR AN IMPROVEMENT IN THE METHOD OF HANGING DOORS. Aaron B. Carpenter. Claim."I do not claim to have invented any of the parts herein described and shown, except as follows: "I claim as new and of my own invention, the application of the movable hanging stile, hinged in a rebate in the doors or sash stile, and steadied in a groove in the jam by screws, either without or in combination with the springs H and K, and roller I, and inclusive of any variations arising from the nature of the particular case, when such application and combination of variations, for the purposes herein described, are substantially the same in construction and practical effect, and shall be used in hanging or mounting French sashes, casement windows, or folding doors, of any description and for any purpose." The casement, sash, or folding doors, instead of being jointed to the permanent frame, are hung to a "stile," which slides in a rebate, and provided with springs that force together the two halves of the door, or sash, when closed, to insure a close joint, FOR AN IMPROVED METHOD OF OPERATING THE DROP CUT-OFF VALVES OF STEAM ENGINES. Frederick E. Sickels. The patentee says: By the method now practised of operating the drop cut-off valve, the motion is derived from the lifter, which approaches its state of rest as the piston of the engine approaches the middle of its stroke, or its maximum velocity, and the valve is tripped by the same motion which lifts it, so that there must be very great nicety in the adjustment to regulate the extent of the cut-off at about the half stroke. The object of my invention is to remedy this, and its principle or character consists in tripping the valve by a motion indepen. dent of the motion of the lifting-rod or rods. And, also, in combining the various parts in such manner as to regulate the cut-off with accuracy during the action of the engine, by connecting the two shafts that trip the two cut-off valves end to end, by means of adjustable spring arms that take into, and are, when set, held in the teeth of a sector, which vibrates on the axis of motion of the shafts, and receives its vibratory motion from the eccentric,-which spring arms may be shifted in the teeth of the sector, brought nearer to, or farther from each other, and thus cut off at a less or greater portion of the stroke." FOR A METHOD OF CASTING THE STEAM CHESTS WITH THE CYLINDER, AND WITH THE CYLINDER BOTTOM AND CONDENSER. Frederick E. Sickels. The patentee says:" In forming the connection of a steam cylinder with the steam chests-of puppet valve engines, it has long been known to engineers, that the closeness of this connection is important in an economical point of view, not only on account of the weight and cost of materials employed in making à long connection, but because all the steam contained in this connection is condensed or otherwise lost at each stroke of the engine: and hence various devices have been resorted to by engineers to surmount this difficulty-the steam chest has been variously arranged and located; but still all these devices have presented a large area between the chest and the cylinder, for the steam chest being cast separate from the cylinder, sufficient room must be left to form the connection by bolted flanches, which necessarily occupy much room. To remedy these evils is the object of my invention, the nature of which consists in casting the steam chests in one piece with the steam cylinder, or one with the cylinder and the other with the condenser and the cylinder bottom, by making the side of the cylinder the side of the steam chest, and so of the condenser; and also in so forming and adapting the appendages of these parts as RECENT AMERICAN PATENTS. to enable them to come together, and to unite the cylinder head with the cylinder, and the cylinder bottom with the narrow compass left between the steam chest and cylinder where they are brought in such close proximity. The flanch on the cylinder and cylinder bottom being dispensed with towards the steam chest, and instead thereof a joint made between the chest and cylinder by packing or driving, and screws inserted from the inside of the steam chest and screwing into the solid metal of the cylinder, form the lower steam chest, and for the upper end, recesses being made in the side of the steam chest to admit the requisite screw bolts for screwing the cylinder head. "I do not claim letters patent simply for casting the steam chests with the cylinder, or with the cylinder bottom and condenser; bu what I do claim as my invention, and desire to secure by letters patent, is casting the steam chests with the cylinder, or one with the cylinder and the other with the cylinder bottom and condenser, by making the side of the steam chest the side of the cylinder or condenser, in combination with the manner of fitting the cylinder head and the lower end of the cylinder to the chests, and the mode of making the attachments without the continuation of the flanches, thus dispensing with the nosles and nosle flanches and their attachments, and saving at each stroke the steam contained in the nosles, all as herein described." FOR A MACHINE FOR GRINDING SPIRAL KNIVES. William Hovey. The patentee says:-" The nature of my invention consists in attaching the twisted (sometimes called spiral) blades or cutters to a flanch projecting from a stock hung on journals in a traversing carriage, so as to present the back of the cutter to be ground to the action of a grindstone, or other reducing or polishing wheel, so that as the cutter on the carriage traverses lengthwise, it shall vibrate freely on the axis of the stock to which it is attached, to follow the twist of the blade, and grind it to a sharp edge, such as is required in cutting, by impinging the cutting edges against the surface of a cylinder by the rotation of the two cylinders or the cutting cylinder on a plane, the cutting being effected by a pressure towards the centre of the axis of the cylinder of knives. The reciprocating motion of the cutters during the traverse motion, being governed by the spiral or twisted surface of the knife itself or anything analogous thereto. "What I claim as my invention, is giving to the spiral, or twisted, knife, or cutter, attached to a flanch in a line radiating (or nearly so) from the axis of the stock, a traversing motion in the direction of its axis, 571 in combination with a réciprocating rotary motion on its axis, when this latter motion is governed by the twisted plane of the cutter, or anything essentially the same, to enable the grinder to give the required level to the ground face, and the proper line to the edge, substantially in the manner herein described." FOR AN IMPROVEMENT IN THE METHOD OF MAKING CONTINUOUS PERCUSSION PRIMERS FOR FIRE ARMS, AND IN THE LOCK THEREFOR. Edward Maynard. Claim."What I claim as my invention, and as distinguished from all other things before known, is-first, making primers of fulminating mixtures, or such compounds as ignite by percussion, in a continuous series, each primer, or any two or greater number, being separated from the others by a substance which is less combustible than the fulminating mixture, by which one or more may be exploded without communicating fire to the others. "Secondly, the mode described of moving and measuring out the primers, by the movement of the lock, substantially as described." FOR AN IMPROVEMENT IN THE METHOD OF DRIVING SPINDLES, FLYERS, OR BOBBINS OF SPINNING MACHINES. William Baxter. The patentee says:-"No part of the operation of spinning has been attended with so much difficulty as that of driving the flyer or bobbin, on account of the great velocities required and the delicate texture of the fibres under operation, for high velocities tend to produce variations in the rotating body, particularly if not made perfectly true, which break the threads and thus retard the operation, and render the spinning of fine threads impracticable. Cog wheels have long since been considered inapplicable to the driving of spindles or bobbins under high velocities, and belts applied as heretofore, tend, by the necessary strain required to prevent slipping, to increase, nay, to produce unsteadiness of motion and much friction, and consequent wear of the parts, soon resulting in unsteadiness of motion and in a waste of power. Efforts have been made to overcome these great practical difficulties by resting the edge of the bobbin or warve of the spindle, on the periphery of a wheel, or on a round belt; but when thus driven, great velocities tend to lift or throw up the bobbin or spindle, there being no provision for preventing so injurious an effect. The object of my invention is to remove all these difficulties, by means of an arrangement which consists in driving bobbins or spindles by a belt, which is embraced by two flanches on the warve, the belt being so arranged as not to press against the periphery of the warve, but merely to hold the bobbin or spindle in suspense by the two flanches, the space between which is equal to the width of the belt, to prevent any vertical movement." Claim." I do not claim as my invention making the warves of spindles, flyers, or tubes for carrying bobbins or spools, with flanches, nor the driving of them by a belt; nor do I claim driving spindles, flyers, bobbins, or spools, &c., by resting them on a belt, as all these devices and methods have been known and used before, but not as I have applied them; and, therefore, what I claim as my invention, and desire to secure by letters patent, is driving spindles, flyers, bobbins, or spools, &c., by means of a belt with parallel edges equal (or nearly so) in width to the space between the flanches of the warves, and passing between them, when these warves are so arranged as to be suspended thereon, without the belt bearing against their peripheries, for the purpose and in the manner substantially as herein described." FOR AN IMPROVEMENT IN FRICTION MATCHES. Stephen Blaisdale. Claim. "What I claim as my invention, is the manufacture of friction matches by dipping the matches into a compound of sulphur and phosphorus, formed into a paste or fluid, by means of glue or any other glutinous or viscid substance as herein set forth." FOR A COMPOSITION OF MATTER FOR COVERING SHIPS' BOTTOMS. S. Williams. The patentee says:-"The materials are varnish, boiled oil, arsenic, red lead, sulphur, and sugar of lead, to which may be added any ochre or other colouring substance, according to the fancy of the person using the same. The proportionate quantity of each material is as follows: Half a gallon of varnish. Two pounds of red lead. Half a pound of sugar of lead. To which may be added, if a copper colour is required, one pound of yellow ochre, and a small quantity of lamp black. These several quantities of ingredients will make about a gallon of the composition. This composition is applied to the vessel while it is boiling hot, and with brushes, in the same manner as ordinary painting." FOR A COMPOSITION FOR RENDERING CLOTH, &C., WATERPROOF, WITHOUT LOSING THE PLIABILITY. Nathaniel Hatch. The following is extracted from the specification, viz. :-"Take half a pound of gum shellac, and one pint alcohol, and put them in a tin-kettle with a cover, and suspend the kettle with said contents in a boiler of boil. ing water, and keep the heat up till the gum dissolves, then put one quart of boiled lin. seed oil in the kettle with the shellac, and boil them together till they are well mixed. Secondly, take one ounce of India rubber, cut it in very small pieces, and one quart of spirits of turpentine, and put them in another tin kettle with a cover, as before named, and suspend it, with the contents, in a boiler of boiling water, and keep the heat up till it is dissolved; then put two quarts of boiled linseed oil in the kettle with the rubber, and keep the heat up until they are completely mixed. Thirdly, take one pound of yellow hard soap, and two quarts of water, and boil them together till the soap is all dissolved. "Then, to make the composition, take 8 lbs. white lead ground in oil, 1 gill coal tar, 6 ounces lamp black, 1 lb. gold litharge, 4 quarts boiled linseed oil, 3 quarts of the above named solution of India rubber, 1 gill of the solution of shellac, as above named, 1 pint of copal varnish, and mix them all well together. Then put one quart of the soap and water in the composition while the soap and water are boiling hot, and stir them together till the whole is completely mixed together, and then apply the composition to the cloth with a common paint brush, and when the cloth is nearly dry, so that it will not rub off, apply the second coat of the composition, and when the second coat is nearly dry, apply the third coat of the composition, which makes the cloth waterproof and pliable. If I want to make any other colour, I put other coloured paint in, enough to make such a colour as I want, namely to make yellow, I take chrome yellow; or for green, I take chrome green; and to make white, I leave out the lamp black, &c." ON THE STEAM VACUUM AS A SOURCE OF POWER. Sir, I am much obliged to your correspondent, Mr. Bashforth, for his reference to the Civil Engineer and Architect's Journal, with the papers in which, his own particularly, I have been much interested. The expression he there gives for the power required is the same as mine. As regards my calculations for the amount of steam required, it simply comes to this;-that I consider that the mere frictions, &c., of the air-pump and steam-engine would alone require the theoretical power to be doubled, and W t |