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IMPROVED DOUBLE BARREL AIR-PUMP.

Sir, My attention having been lately turned towards the improvement of the air-pump,and having nearly completed one upon a considerable scale, I takethe liberty to send you the accompanying drawings with the following description, to which I hope you will give a place in your valuable publication. I am but an amateur mechanic, with, however, the advantages of good tools and leisure time. I employ two barrels, and, I think, the action of the pump will be found both simple and effective.

Fig. I represents a section of one of the barrels with piston and rod, box and oil cup complete. The valve in the top plate in that position, cannot be properly illustrated.

A is the barrel 10 inches, clear bore of 2 inches diameter, and of an inch thick of brass.

B the pedestal, 44 inches square and I inch thick, into which the barrel is screwed to the depth of half-an-inch. The end of the barrel has a channel a sunk into it, to receive a collar of elastic gum, which, on screwing down the barrel will secure the joint, and is preferable to oiled leather. The part next the channel, and also the shoulder b, are very accurately turned, so as to fit almost air-tight themselves. The aperture marked c, is a bore communicating to the pipe leading to the pump-plate; the connected joints will be seen in another of the figures hereafter described.

C the piston, consisting of two parts, screwing into each other for the purpose of tightening the oiled leathers which fills the space dd. The piston is 1 inch deep, and is bored in a conical form to receive the plug valve e, which is fitted very accurately, so as to be perfectly air tight on being drawn up. The leathers are turned to fit the barrel, and in order to preserve as much as may be their elasticity, when the pump is not in use, I have widened a very little the bore of the lower part of the barrel for the space of an inch, which will relieve the leathers from being constantly under strong pressure, and ensure their due fitness when worked.

D is a steel collar screwing on to the piston rod, and forming a continuation of the brass cone of the plug valve--having also four lugs, or ears, as seen in the larger drawing E, Fig. 2. These lugs

form portions of a larger cone, and serve to press down the piston when at the top of the barrel, acting on the face of the piston. The spaces between the lugs (n) permit the air to pass through the piston at the downward stroke, depressing the plug valve from its socket about the thirtieth part of an inch, which is sufficient to allow the air to expand itself into the barrel without any resistance.

F the piston-rod, say inch in diameter, of shear steel, very accurately turned and polished, screwing at its lower end through the steel collar D, and into the plug valve e, both of which were turned true upon the rod.

G the top plate, forming a circle of 4 inches in diameter, and half-an-inch in thickness, with a screw part 4 of an inch deep screwing into a channel cut in the top of the barrel. In the bottom of the channel is placed a collar of elastic gum, which, receiving pressure by the screw, makes the joint secure. In the centre of the top plate ƒ is turned a conical hollow to receive the cone of the steel collar, and a small part of the plug valve with channels also cut for the four lugs, so that on the piston being drawn up, the top (ground very true) strikes the under face of the top plate, which is turned as true as possible, so as to admit of the closest contact. The air will thus be discharged through the upper valve so nearly as only to leave the minute portion that will remain betwixt the faces of the lugs and that of the piston, and they having only about the area of onetenth of an inch, while the space betwixt them and the piston is only the thirtieth part of an inch, the disadvantage may be said to be inconsiderable when the great area of the barrels is taken into account. The action of the piston is simple, as the operator has only to ascertain that it comes into contact with the top plate, which will determine itself and be confirmed by the falling of the valve, provided the lever be properly adjusted. It is not necessary that the piston should reach the bottom of the barrel.

H, the stuffing-box filled with collars of oiled leather, screwed down tight by the oil cup I. The box is 1 inch inner diameter, and 2 inches high, and allows room on the top plate for the discharging valve to work direct into the barrel.

K, the discharging valve-fitted very accurately, and having a mortice cut

through the stem to receive a friction roller and the working lever, as shown in fig. 3. The smaller part of the stem is fitted into a guide socket (g) in the frame (h) so as to ensure its vertical action, having an elastic wire to return the valve smartly, at the instant that the face of the piston touches the top plate. In this sketch nothing is shown but the valve and its appurtenances. It is worked by a wire rod, fixed to the head of the piston rod by an arm, and has a hinge which lifts the lever on the rise, and passes over it on descending; the lever works in a mortice in the pillar (m). L, shows the piston rod, head, and arm for the lever wire. The rack is attached to it by a steel pin, and the piston rod, when screwed into the head, is secured by a pin from the possibility of getting loose, and thereby deranging the working of the piston valve collar.

Fig. 7 is a plan of one of the pedestals, showing the mode of communication with the pump-plate pipe. The part M is screwed by Smeaton's union joint to the angular pipes screwed to the pedestals. N is a stop screw, shown on a larger scale, fig. 4, as given by your correspond. ent, S. K., No. 349, vol. 13. The bore P leads to a neck, into which is inserted the pipe leading to the plate. The joints are all secured by collars of elastic gum.

The pump plate is 9 inches in dia

meter, and I use the stop-cocks with stuffing boxes, as suggested by S. K. The rotary motion proposed by your Exeter correspondent, H. I., No. 244, vol. 9, appears to me to be objectionable as not being sufficiently controulable, and as having the encumbrance of another wheel, and a greater length of racks. I prefer the wheel and racks (with epicycloidal teeth) and a lever with two handles. The barometer and syphon guages are attached in a more simple manner than Cuthbertson's.

Fig. 6 is a section of the chuck I use for screwing tight the piston leathers, and turning them in the lathe.

V, is the chuck, of hard dry wood, with a screwed socket for the mandril. Through the centre is put an iron bolt x, a little squared, so as not to turn round, the outer end tapped to receive a nut. A cone W, is turned to fit exactly into the piston, and two small brass pegs (N) are inserted outside the base of the cone to fit into corresponding holes drilled in the bottom of the piston, to prevent its moving when screwed up. A sufficient number of leathers are then screwed tight, and a wooden washer, turned true, is put next the face of the piston previous to screwing on the nut, which keeps it firm enough for turning. Two holes are also drilled in the strongest part of the piston face to receive the prongs of a

s+Si

and D () will be the numbers

for Scotland and Ireland. It now only remains to assign a proper value for the arbitrary quantity i. Now, let it be remembered that, in point of importance, we have supposed that an Englishman, a Scotchman, and an Irishman, are each of the same value.. the only value that we can rationally assign for i is the quotient produced by dividing the whole amount of the taxes by the united popu

CORRUPTIONS OF THE ENGLISH TONGUE.

Sir, I did not anticipate that my letter (written on January 20th, and inserted on March 31st) in the Mechanics' Magazine, on the Corruptions of the English Tongue, would have led to any occasion of again addressing you. A learned Theban has, however, taken up the cudgels on the side of the corruptionists, in the columns of a weekly review called the Literary Guardian, and attempted to bolster up their cause with divers apologies for arguments, and that withal in so confident a style, that I really must trespass on your indulgence once more, and give the poor man the good sound drubbing he deserves. It is true, he seems to have been, in the very moment of perpetration, rather afraid of punishment for his presumption, and therefore edges in a sort of half-compliment to the Mecha

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nics' Magazine at the same time; attributing its insertion of the letter in question to an 66 over-anxiety for popularity." Popularity indeed!-as if the other side were not, unfortunately, the more popular of the two, and as if it did not require a sort of chivalry on the part of an editor, now-a-days, to admit of any communicaunmeaning verbiage which threatens to tion attempting to stem the torrent of swamp our language. The idea is worthy of the article which it commences, and only to be surpassed in absurdity by the "argument" which follows.

This is one of mine adversary's "great guns;" and, as might be expected from an advocate of corruption, is ridiculous on the very face of it. Only think of an animal of any pretensions to rationality asking the question, "Why is the English language not the language of England?" He might as well have asked, "Why is the writer of the paper in the Literary Guardian, on Scientific Nomenclature, not an ass?"-and the reply would be much the same in both instances. Only think for a moment of the stupidity of the idea, that because the English language is partly composed of words from foreign sources, it is therefore not "the language of England." And only think again of the ultra-stupidity of the other notion, that because, when the English language was in process of formation, our ancestors borrowed some words and phrases, expres sive of new ideas, from the neighbouring nations, we are to go on 66 dragging in" words and phrases from any tongue on the face of the earth, although we may have terms quite as expressive of the idea, or more so, in the "pure well of English undefiled." Cannot I as well say that this notion is sheer "nonsense," as borrow a word from the Irish, and brand it as "blatherumskate ?" Is it not as well to call an idiot "an idiot" at once, as to entitle him a "Lit-Ree-gah-diang,” which, for aught I know, may be the Chinese for that indispensable word? Is an English serjeant of grenadiers, if he pleases, to give the word to his men, "shoulder tic-tic-boos;" and then, if they do nothing, have them flogged for disobeying orders, because they ought to have known that "tic-tic-boo" was Sandwich-islandish for a musket, and, being Sandwich-islandish, was of course English, as soon as he chose to make it so? In fact, would the men be flogged, or the sergeant sent to Bed