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firable circumftance, that the ivory pipe of the hy- 
grometer fhould be the thinned: poffible ; in order that 
it might be more readily affedted. This I had fore- 
feen, before I had learnt it from experience; but I 
was afraid of its being attended with ftill greater in- 
conveniences than that it was intended to remedy ; 
from the adtion of the mercury againft pipes whofe 
fides would be thinner. However, this might be tried. 
In the mean time, I fancy that, for obfervations in 
which it is abfolutely neceflary that the internment 
fhould eafily be affedted, lefler hygrometers might 
be made, whofe tubes containing a lels quantity of 
mercury, would refill: the adfion of it, though with 
a lefs degree of thicknefs. (Perhaps it would not 
be impoffible to ufe tubes made of fome very thin 
quills.) I cannot yet afcertain whether thefe little hy- 
grometers could be graduated by themfelves, or whe- 
ther they muff be compared with thofe of which 
I have given the dimenfions ; this we lhall learn 
from experience. 
94. The difference there is between the heat and 
the difcrete humor in the power of diffufing itfelf, oc- 
cafions in another refpedt a confiderable difference in 
the goings of the thermometer and hygrometer. 
The heat is brought into a date of equilibrium much 
fooner and with much greater certainty than the 
humor. Two thermometers accurately condrudted 
and fixed near each other, in a place where the heat 
does not change very fuddenly, always agree to- 
gether. This is not the cafe with two hygrometers: 
they feldom agree, that is, they feldom prefer ve the 
fame conformity to each other, when there is the 
leaf!: variation in the humor : at fome times their 
difference increafes, at others it diminifhes ; this can 
only 
