Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses. With observations and inquiries thereupon / By R. Hooke.

Robert Hooke

Date:: 1665

Credit: Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses. With observations and inquiries thereupon / By R. Hooke. Source: Wellcome Collection.

343/384 page 223

$in the box, till the furface of that within the Tube be equal to it, for the Quickfilver ( as I have clfewhere prov’d ) being more heterogener ous to the Glafs then the Air, will not naturally rile upfo high within the fmall Pipe,as the fuperftcies of the Mercury in the box s and therefore you are, to obferve, how much below the outward fuperftcies^of the Mercury in the box, that of the fame in the Tube does ftand, \yKen the top being open, free ingrefs is admitted to the outward Air. ' ; ^ ■j aJI Having thus done, I permitted the Cylinder, or fmall Pijie,;p?:rifq out of the box, till I found the furface of tlm Quickfilver in the Pipe tp^e two inches above that in the box, and found the Air to have expanded it felf but one fixteenth part of an inch* then drawing up thttJ final} pipe, till I found the height of the Quickfilver within to be fqii^^hys above that without, lobierved the Air to be expanded onlyj of an inch more then it was at firft , and to take up the room of 17 inch: then I railed the Tube till the Cylinder was fix inches high, and found the Air to takeup if inches of room in the Pipe's then to8, i^Q[2. &c< the expanfion of the Air that .1 found to each of which Cylinders are fet down in the following Tables where t]ae firft row figfnfies the height of the Mercurial Cylinder 5 the next,°the expanfion of 'the Air s the third, the prefliire of the Atn/ofphere,^ or the higheft Cylinder oi Mercury, which was then peer thirty inches : The Lift fignifies tjie force of the Air fo expanded , which is found by fubftratting the ftfft row of numbers out of the third s for having found, that the outward Air would .then keep up the Quickfilver to thirty inchys, look whatever of that height is wanting muft Re attributed to the Plater of the Air depreffing. And therefore having the Expanfion in the l&ond row,and the’ height ot the fubjacent Cylinder of Mercury in the fitftpand the greateft?height of the Cylinder of Mercury0 which of it felf counterballances the whole prefliire of the Atmofpher'e s by fubftra&ingftie numbers of the firft row V‘KV' ~ -r-j- panfions, regiftred. t ,c 1 ' n “iC The onfequently the foreojpj' the Air,in the feye V, ■ ho og - kSa 02 4^0 dbg * °c i°i -$S + 02 otd 1$