Micrographia: Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries ThereuponHooke, Robert
History
Micrographia: Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon
Hooke, Robert
Magnifying glasses -- Early works to 1800; Microscopy -- Early works to 1800; Natural history -- Pre-Linnean works
But these are but conjectures also, and must be determin’d by such kind of
Observations as I have newly mention’d.
Nor will it be difficult, by this _Hypothesis_, to salve all the
appearances of Eclipses of the Moon, for in this _Hypothesis_ also, there
will be on each side of the shadow of the Earth, a _Penumbra_, not caus’d
by the Refraction of the Air, as in the _Hypothesis_ of _Kepler_; but by
the faint inlightning of it by the Sun: For if, in the sixth Figure, we
suppose ESQ, and GSR, to be the Rays that terminate the shadow from either
side of the Earth; ESQ coming from the upper limb of the Sun, and GSR from
the under; it will follow, that the shadow of the Earth, within those Rays,
that is, the Cone GSE, will be totally dark. But the Sun being not a point,
but a large _area_ of light, there will be a secondary dark Cone of shadow
EPG, which will be caus’d by the earth’s hindring part of the Rays of the
Sun from falling on the parts GPR, and EPQ, of which halved shadow, or
_Penumbra_, that part will appear brightest which lyes nearest the
terminating Rayes GP, and EP, and those darker that lye nearest to GS, and
ES: when therefore the Moon appears quite dark in the middle of the
Eclipse, she must be below S, that is, between S and F; when she appears
lighter near the middle of the Eclipse, she must pass some where between RQ
and S; and when she is alike light through the whole Eclipse, she must pass
between RQ, and P.
* * * * *
Observ. LIX. _Of multitudes of small _Stars_ discoverable by the
_Telescope_._
Public-domain text, read in full here on John Shaqi.
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