The origin and progress of the mechanical inventions of James Watt; illustrated by his correspondence and the specifications of his patents. Letters ... specifications of patents, appendix Volume 3 - Softcover
Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1854 edition. Excerpt: ...prout ibidem observatum est; unde requiritur ut artificio aliquo prospiciamus, ut decrescente sic vi motrice, resistentia itidem mimiatur, quo possit usque ad finem a dicta vi motrice superari; quemadmodum in horologiis Reprinted from the ' Acla Eruditorum LifBioj' for 1690, im 410-414. precautions there specified, there always remained in the tube about a fifth part of the air usually contained in it. Whence a twofold inconvenience arises: viz. 1st, that in this way we lose half of the desired effect, so that scarcely can 150 Ibs. weight be raised to the height of one foot, when otherwise 300 Ibs. ought to have been raised, if the tube A A had been perfectly emptied; and 2ndly, that as the piston gradually descends, the force which makes it descend is itself diminished, as was also observed in the passage already referred to, so that we have to provide, by some contrivance, that, as the moving force thus decreases, the resistance may in like manner decrease, so that it may be overcome by the aforesaid moving force until the end: just as in watches the unequal portatilibus vis inaequalis laminae elasticae totam machinam moventis certa arte ita temperatur, ut per totum decursum sequali facilitate rotarum resis-tentiam vincat: longe vero commodius foret, si vis movens a principio usque ad finem semper remaneret sequalis. Nonnulla igitur in hunc finem jam pridem tentata sunt, quo posset vacuum, pulveris pyrii ope, perfectum obtineri; sic enim, nullo aere infra pistillum resistente, tota atmos-phasraa columna super incumbens dictum pistillum aequali vi nsque ad fundum deprimeret. Sed frustra hactenus huic negotio insudatum est, sem-perque quinta circiter pars aeris in tubo A A force of the main-spring, which moves' the whole machine, is so regulated...
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