Micrographia - Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon by Robert Hooke
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page 27 of 465 (05%)
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therefore to procure and cast a sufficient quantity of light on an
Object in the night, I thought of, and often used this, Expedient. I procur'd me a small Pedestal, such as is describ'd in the fifth Figure of the first _Scheme_ on the small Pillar AB, of which were two movable Armes CD, which by means of the Screws EF, I could fix in any part of the Pillar; on the undermost of these I plac'd a pretty large Globe of Glass G, fill'd with exceeding clear Brine, stopt, inverted, and fixt in the manner visible in the Figure; out of the side of which Arm proceeded another Arm H, with many joynts; to the end of which was fastned a deep plain _Convex glass_ I, which by means of this Arm could be moved too and fro, and fixt in any posture. On the upper Arm was placed a small Lamp K, which could be to mov'd upon the end of the Arm, as to be set in a fit posture to give light through the Ball: By means of this Instrument duly plac'd, as is exprest in the Figure, with the small flame of a Lamp may be cast as great and convenient a light on the Object as it will well indure; and being always constant, and to be had at any time, I found most proper for drawing the representations of those small Objects I had occasion to observe. None of all which ways (though much beyond any other hitherto made use of by any I know) do afford a sufficient help, but after a certain degree of magnifying, they leave us again in the lurch. Hence it were very desirable, that some way were thought of for making the Object-glass of such a Figure as would conveniently bear a large Aperture. As for _Telescopes_, the only improvement they seem capable of, is the increasing of their length; for the Object being remote, there is no thought of giving it a greater light then it has; and therefore to augment |
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