Hygromeiry . 2 1 
tearing from them thin fafciculi of fibres ; which operation is 
eafy in fome, as /&<?«/>, whalebone , and ga/, but very difficult iu 
others, as quill and fome forts of wood. 
o 2 . The firft hygrofcopes of the clafs of threads, which I 
obferved comparatively to the clafs of flips, were of hemp, gut, 
whalebone, and fome woods, and they exhibited a phenome- 
non which at firft I could not underftand : when they were 
expofed with the Jhps in damp air ; as, for inftance, in open air 
during the fecond period of dew above determined, or in a 
glafs veflel inverted over water ; the threads had only very 
fmall motions backwards and forwards round their point deter- 
mined in water, while the flips had confiderable motions within 
that point, without coming near it, if the temperature was fen - 
fibly above freezing point. Thence arifes the objection againft 
the general propofition above ftated : for thefe two claffes of 
hygrofcopes contradicting one another on the changes of moiflure, 
nothing could be afferted in that refpeft, till there were fuffi- 
cient reafons to exclude one of thofe claffes of informers, and 
to truft the other clafs. 
33. Proceeding to multiply the fpecies of thofe two claffes 
of hygrofcopes, I found always the lame fundamental march m 
flips, all of them conftantly moving in the fame dire&ion ; but 
in multiplying the fpecies of threads , 1 found fuch variety 
between them, that in their own clafs they created diftruft ; 
fome of them, as of deal, aloes pitta, liber of lane tree, quill, 
and thin flems of gramen, in coming out of water , increafed ill 
length . they went farther that way, to a certain point, as the 
air was dryer : they retrograded then with accelerated fteps, 
when drynefs increafed, thereby returning to the point where 
they had flood in water ; and they continued to move in the 
fame retrograde way, with great acceleration, by a ftill in- 
creafing 
