Page:Micrographia - or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon.djvu/70

Rh round Spring (the way of making which trials is obvious enough.) And with the fluid bodies of Mercury, Air, &c, the way of trying which, will be somewhat more difficult; and therefore I shall in brief describe it. He therefore that would try with Air, must first be provided of a Glass-pipe, made of the shape of that in the fifth Figure, whereof the side A B, represents a straight Tube of about three foot long, C, represents another part of it, which consists of a round Bubble; so ordered, that there is left a passage or hole at the top, into which may be fastened with cement several small Pipes of determinate cylindrical cavities: as let the hollow of

There may be added as many more, as the Experimenter shall think fit, with holes continually decreasing by known quantities, so far as his senses are able to help him; I say, so far, because there may be made Pipes so small that it will be impossible to perceive the perforation with ones naked eye, though by the help of a Microscope, it may easily enough be perceived: Nay, I have made a Pipe perforated from end to end, so small, that with my naked eye I could very hardly see the body of it, insomuch that I have been able to knit it up into a knot without breaking: And more accurately examining one with my Microscope, I found it not so big as a sixteenth part of one of the smaller hairs of my head which was of the smaller and finer sort of hair, so that sixteen of these Pipes bound faggot-wise together, would but have equalized one single hair; how small therefore must its perforation be? It appearing to me through the Microscope to be a proportionably thick-sided Pipe.

To proceed then, for the trial of the Experiment, the Experimenter must place the Tube A B, perpendicular, and fill the Pipe F (cemented into the hole E) with water, but leave the bubble C full of Air, and then gently pouring in water into the Pipe A B, he must observe diligently how high the water will rise in it before it protrude the bubble of Air C, through the narrow passage of F, and denote exactly the height of the Cylinder of water, then cementing in a second Pipe as G, and filling it with water; he may proceed as with the former, denoting likewise the height of the Cylinder of water, able to protrude the bubble C through the passage of G, the like may he do with the next Pipe, and the next, &c. as far as he is able: then comparing the several heights of the Cylinders, with the several holes through which each Cylinder did force the air (having due regard to the Cylinders of water in the small Tubes) it will be very easie to determine, what force is requisite to press the Air into such and such a hole, or (to apply it to our present experiment) Rh