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Hooke, Robert, 1635-1703 / Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses : with observations and inquiries thereupon
(MDCLXVII [1667])

Observ. XXVII. Of the beard of a wilde oat, and the use that may be made of it for exhibiting always to the eye the temperature of the air, as to driness and moisture,   pp. 147-152

Page 147

             M iCROG R AP HIA.                                      47
reriding within them might be liflolv d and mix'd with the ambient juices
of that place, and thereby thofefbres and tender parts adjoyning be-
come afeifed, and as it were corroded by it ; whence, while that afti-
on latis, the pains created are pretty {harp and pungent, though fmall,
which is the eflential proper ty of an itching one.
  That the pain alfo caufed by the fiinging of a Flea, a Gnat: a Flie a
Wafp, and the like, proceeds much from the very fame cauie, I elsewhere
in their proper places endeavour to manifeil. The ftinging alfo of (bred
Horf-hair, which in meriment is often ftrew'd between the fbeets ofa Beds
feems to proceed from the lame caueI .
Obferv. X X V I I. Of the Beard of a wilde Oat, and the ufe that
   may be made of it for exhibiting always to the Eye the temperature
   ofthe Air, as to drinefi and mooiurei
IHis Beard of a wild Oat, is a body of a very Cutious f1ruatirethough
Tto the naked Eye it appears very flight, and inconfiderable, it being
only a fiball black or brown Beard or Briftle,which grows out ofthe fide
of the inner Husk that covers the Grain of a wild Oat~the whole length of
itwhen put in Water, fo that it may extend it felf to its full length,is
above an Inch and a halfandfor the moft part fomewhat fborter,but when
the Grain is ripe, and very dry, which is ufualy in the Moneths of 7Ugy,
and Augxfl, this Beard is bent f6mewhat below the middle, namelyabout
' from the bottom of it, almoft to a right Angle, and the under part of
it is wreath'd lik a With ; the fubftance of it is very brittle when dry,
it will very eafily be broken fromu the husk on which it grows,
  If you take one of thefe Grains, and wet the Beard in Water,you will
prefently fee the [mall bended top to turn and move round, as if it were
=enible; and by degrees, if it be continued wet enough, the joint or knee
will ftreighten it felf; and if it be fuffer'd to dry again, it will by degrees
move round another way, and at length bend again into its former
  Ifit be view'd with an ordinary fingle Mfcrofcope, it 'will appear like
a fmall wreath'd Sprig, with two clefts ; and if wet as before, and
then look'd on with this Microfcope, it will appear to unwreath it felf,
and by degreesto ftreighten its knee, and the two clefts will become
fireight, and almoft on oppofite fides of the fmall cylindrical body.
  If it be continued to be look'd a little longer with a Mict-ofcoe, it
will within a little while begin to wreath it aelf again, and foon after
return to its former poflure, bending it felf again neer the middle, into
a kind of knee or angle.
   Several of thofe bodies I examin d with larger Microfcopes, and there
found thenm much of the make ofthofe two long wreath'd cylinders de-
lineated in the fecond Figure of the I 5. scheme, which two cylinders re-
                                       x X                  prektnt

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