Hygrom&iry. 37 
medium. But that furmife cannot be admitted when th e flips of 
fuch difiimilar fubftances as whalebone, quill, and deal, fenfibly 
agree in their motions at that period, and when a number of other 
ftps of the vegetable and animal kinds follow alfo the fame 
general march. 
55. In refpedl of the threads, which are the only caufe of 
the above doubt, my theory, which removes it, is alfo con- 
firmed by that experiment. That caufe of doubt is exemplified 
in the table by the thread of whalebone, which has almoft no 
motion, while its Jlip moves from 85 to 100. At that period 
of moifture, no regularity can be expected from experiments 
made in clofe veffels ; by which circumftance, not having the 
correfpondent obfervations of 'weights, it cannot be d^mon— 
ftrated by immediate experiments, that the thread of whale- 
bone is then fltationary from its nature ; but the threads of 
quill and deal, which are in that ftate during the regular courfe 
of the experiment, will guide us in that enquiry. The thread 
of quill is jlationary during that great part of the obferved in- 
creafe of moiflttre, by which the thread of whalebone moves 
from 1 to c 1 ~ , 6 1 the thread of deal is alio jlationary, while 
the fame thread moves from 7 1 t0 9 1 ’ 3 ‘ They both after- 
wards retrograde - , the quill from ioj to 100 , and the deal 
from 122,6 alfo to 100 and it is during the latter part of that 
retrogradation, correfpondent to a continued direSl motion of 
the flips, that the thread of whalebone, and fome more of its 
clafs, after a very decreaflng march comparatively with all the 
flips, are at laft flationary, and then a little retrograde. In that 
Jtationary ftate of the threads, while moifture proceeds in the 
lame direction, they move backwards and forwards, more or 
lefs, according to the duration of that ftate, and to t*»e quan- 
tity of the retrogradation. This may be feen by the taoie, in 
