A Description of an Air-Pump of a New Construction, with an Account of Its Performance, and of Some Experiments and Observations Tending to Ascertain the Circumstances on Which the Perfection of That Machine Depends, and to Render Its Theory More Compleat

James Little
1797 Transactions of the Royal Irish Academy  
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more » ... out Early Journal Content at http://about.jstor.org/participate--jstor/individuals/early-journal--content. JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not--for--profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact support@jstor.org. the year 1785 ; but not finding it to perform as well as I had exP eked, I deviled an alteration and improvement in it, which I had almoft f niIhed the workmanship of in 1788, being that which s21 J which Is here defcribed ; and from that time 'till the 1,a{t fum. mer (1.785 it lay by me negleaed, bad health, &c, diverting my attention from it ; for the whole of it, except the forging the iron-work,was n ade by niyfe 'f without affiftance. At length, being loth to lofe my labour, I put the laft hand to it. Before it was finifhed, I was acquainted with the conitru Lion of Mr. Smeaton's air-pump, with its improve iiz-ents, but had not heard of Mr. Cuthbertfon's ; which, as well as Mr. Smeaton's, I -find is conceived on the fame principle with mine, yet the ap '1ication of that .principle in the machine here 41efcribed, being p g exhibited in a much more Pimple conftru ion, it will I am L 3z4 :i exactly in the middle or axis of the barrel, care was taken that the pofition of the box, and of the focket annexed t it, fhould be fecured, by having a prominent part of the plate of the box of leathers inferted into the pump barrel, and a like projecting part of the lid of the box inferted into the box itf elf ; alfo that the pifton rod fhould mof exactly fill the Pocket in the lid. Over the collar of leathers, within the box, lies a tinned brats plate, which is prefed down upon them by the ends of three (crews 3, 3, fcrewed through the lid of the box. THE piton. is moved up and down by the toothed flat bar or rack F, whole end is furnifhed with an arm G, (to be taken off occafionally which arm is fecured againft a thoulder formed on the end of the pifton rod, by a nut H fcrewed on the rod ; the rack is moved by a finall steel wheel L, one inch and -7in diameter, having twelve teeth, . and which is, turned by the handle X fixed on. its axis L This wheel is fuftained by the cheeks K, K, fig. i. & z. furnifiied with projeting Pockets, through which its axis pares. Thefe cheeks
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