VELOCITY OF WHEELS. Wheels are for conveying motion to the different parts of a machine, at the same, or at a greater or less velocity, as may be required. When two wheels are in motion, their teeth act on one another alternately, and, consequently, if one of these wheels has 40 teeth, and the other 20 teeth, the one with twenty will turn twice upon its axis, for one revolution of the wheel with 40 teeth.--From this the rule is taken, which is,--as the velocity required is to the number of teeth in the driver, so is the velocity of the driver to the number of teeth in the driven. Note. To find the proportion that the velocities of the wheels in a train should bear to one another, subtract the less velocity from the greater, and divide the remainder by the number of one less than the wheels in the train; the quotient will be the number rising in arithmetical progression, from the least to the greatest velocity of the train of wheels. Example 1. What is the number of teeth in each of three wheels to produce 17 revolutions per minute, the driver having 107 teeth, and making 3 revolutions per minute? 17 3 = 14 7, therefore, 3 10 17 are the velocities of three Example 2. What is the number of teeth in each of 7 wheels, to produce 1 revolution per minute, the driver having 25 teeth, and making 56 revolutions per minute? 561= 55 7-1 6 gressional velocities. 9, therefore, 56 46 37 28 19 10 1, are the pro 46: 37 : 28 : S7 :: 37: 49 72 137 1 : 137 : : 10: 1370 which It will be observed that the last wheel, in the foregoing example, is of a size too great for application; to obviate this difficulty, frequently arises in this kind of training, wheels and pinions are used, which give a great command of velocity.-Suppose the velocities of last example, and the train only of 2 wheels and 2 pinions. 18, therefore, 56 19 1, are the progressional ve 19:25:: 56:74 teeth in the wheel driven by the first driver, teeth, in the second driven wheel, 10 teeth 25 drivers 74 driven. and 1 10:19: 190 being in the driving pinion. 10 190 The following is a table of the radii of wheels, from ten to three hundred teeth, the pitch being 2 inches. The radius for any other pitch may be found by the following analogy:-as two inches is to the radius in the table, so is the new pitch to the new radius. TABLE. No. Radius No. Radius No. Radius No. Radius of in of in of in of in Teeth. Inches. Teeth. Inches. Teeth. Inches. Teeth. Inches. TABLE CONTINUED. No. Radius No. Radius of in of No. Radius No. Radius 157 158 60.800 228 72.577 265 84.354 191 154 49.023 192 61.118 155 49.341 156 49.660 193 61.436 194 61.755 49.978 62.073 50.296 195 229 72.895 266 84.673 230 73.214 267 84.991 231 73.532 268 85.309 232 73.850 269 85.627 159 50.615 196 62.392 62.710 161 51.251 198 63.028 162 51,569 199 63.346 75.123 63.665 233 273 86.900 274 87.219 75.760 275 87.537 76.078 168 171 166 52,843 203 64.620 240 76.397 65.893 244 77.670 66.211 245 77.988 282 89.765 66.529 246 78.306 283 90.084 66.848 247 78.625 284 90.402 67.166 248 78.943 285 90.720 67.484 249 79.261 286 91.038 176 55.026 213 67.803 79.580 177 55.344 250 287 91.357 91.675 178 56.662 289 252 80.216 91.993 179 56.980 253 80.534 290 92.312 69.075 69.394 225 71.622 291 254 80.853 92.630 255 81.171 292 92.948 256 81.489 293 93.267 257 81.808 294 93.585 258 82.126 295 93.903 259 82.444 296 94.222 260 82.763 297 94.540 261 83.081 298 94.858 262 83.599 299 95.177 263 83.717 300 95.495 264 84.038 On some kinds of Fulminating Powder inflammable by Percussion, and their use in Fire-arms. By P. W. SCHMIDT, Lieutenant in the Prussian service.* A POWDER, inflammable by percussion, has been used for some The following formulæ years past, especially in fowling-pieces. * From Schweigger's Journal, Band xi. p. 66. have been given for the preparation of this powder, the principal ingredient of which is chlorate of potash. 1. 100 parts of chlorate (oxy-muriate) of potash, 12 parts of sulphur, and 10 parts of charcoal are intimately mixed. The grains are produced by forcing the soft paste through a sieve. 2. 100 parts of chlorate of potash, 42 parts of saltpetre, 36 parts of sulphur, and 14 parts of lycopodium. These are the usual ingredients that have hitherto been mixed with the chlorate of potash for the purpose of making priming powder. The guns, however, with which this powder is used, are very various in their construction. In some it primes itself by means of the mechanism of the lock, passing, on being cocked, into a small conical recess, which communicates with the touch-hole; in others, it is put in previous to every shot. In the former kind of guns a quantity of powder sufficient for a certain number of shots is kept in a recess attached to the lock, called a magazine; and the locks (which were invented in England by Mr. Forsyth) are called magazine locks. In some guns the stroke of the cock, which is in the shape of a hammer, falls immediately on the fulminating powder strewed in the above recess. In order to protect the powder from wet, small balls of it were covered over with wax, and placed sometimes in the conical recess, and at others fixed to the cock itself. In both instances the ball was kindled in the recess just mentioned, by means of the percussion. Besides these, other contrivances have been used for the purpose of igniting this kind of powder; yet they have all their defects, and offer so many difficulties in practice as to have prevented their general introduction. Latterly, they have contrived in Germany to fix the powder in at small case of very thin copper foil, for the purpose of keeping it dry; and for that purpose a cylinder is screwed into the body of the gun instead of the touch-hole, and rests, for the sake of greater support, on the plate of the lock, instead of resting on the pan. The inner space of the cylinder is filled, in loading, with the same powder as that of the charge. The igniting-cap, at the bottom of which is the detonating powder, is, previous to firing, turned up on the cylinder. In this cylinder is a small round aperture, leading to the inner space of the cylinder. On the trigger being pulled, the cock strikes the igniting-cap, and the fulminating powder is kindled by the blow, flows through the aperture, inflames the shot, and breaks the igniting-cap. Mr. Wright seems to have taken great pains with the subject.* He recommends, for the igniting-caps, to use fulminating mercury, saying that sportsmen had justly complained of the powder made of chlorate of potash, since it soon produces the oxidation of the barrel and touch-hole, and the charcoal which remains after the firing, rendering them unfit for use. The advantages of his new powder he enumerates as follows: it does not make the gun rusty so soon as the • Mr. Wright's paper will be found in Phil. Mag. vol. Ixii. p. 203. other; it produces neither dirt nor moisture; it is not so liable to ex plode as the other powder, and if it does explode, its effects are less destructive, inasmuch as its power does not extend so far. The following is his mode of preparation: "I place two drachms of quicksilver in a Florence flask, and pour six drachms (measure) of pure nitric acid on the mercury: this I place in a stand over a spirit lamp, and make it boil till the quicksilver is taken up by the acid; when nearly cool, I pour it on an ounce (measure) of alcohol in another flask: sometimes immediate effervescence ensues, with the extrication of nitrous æther; and often I have been obliged to place the mixture over the lamp, till a white fume begins to rise, when the effervescence follows. I suffer the process to continue (removing the lamp) till the fumes assume a reddish hue; when I pour water into the flask, and the powder is found precipitated to the bottom; I pour off and add fresh water, permitting the powder to subside each time before the water is poured off, so as to free the substance as much as possible from the acid, and then I pour it on a piece of filtering paper, and place the powder in an airy room to dry. It should be kept in a corked (not stoppered) bottle." For the filling of the caps, he makes use of an ivory rod, which has a scoop at one end for the purpose of receiving the powder, and at the other is cut flat; with this he puts in as much fulminating mercury as will cover the bottom; he then dips the flat end into a strong tincture of benzoin, and rubs this substance gently about the case; by which means the powder is set fast and covered as with a varnish. Professor Schweigger, speaking of these kinds of experiments in his chemical lectures, noticed the difficulty of kindling gunpowder by the mere admixture of such substances, as has been shown in a criminal investigation that took place at Munich a few years ago. A box filled with gunpowder was sent to an individual; enclosed were fulminating papers, which were to inflame on the box being opened. Fortunately, however, the murderous design was frustrated; for although the papers exploded, they did not kindle the powder. The assassin was discovered and punished. M. Gehlen, who had been examined at the trial, was led by the circumstance to make several experiments for the purpose of kindling gunpowder by means of Brugnatelli's fulminating silver, but they all failed. It seems that in England, too, difficulties had been found in igniting gunpowder with fulminating mercury; for Mr. Wright observes, if any one doubts the practicability of firing gunpowder by means of fulminating mercury, by procuring a percussion-gun, he may try the experiment and be fully satisfied." Professor Schweigger having, therefore, requested me to try some experiments on this subject, especially with fulminating silver, I made them in the chemical laboratory of our university, and the following were the results. 1. Fulminating silver was prepared in the usual way; five drachms of fuming nitric acid, and five of alcohol were poured over one drachm of fused nitrate of silver. When the effervescence and solution were |