[ 4-31 ] 
that, without perceiving it, a deviation from 80 to 
104, was made in the fpace between the two funda- 
mental points of his thermometer. 
65. If in the lame manner we trace the origin of 
all inftruments defigned for nice menfuration, we 
fhould find that have all been defective at firft, and 
gradually brought to perfection, when men of genius 
have thought them worthy of their attention. Thus 
from the firft watch, which depended entirely upon 
the unequal and uncertain action of a fpring, a luc- 
ceffion of attempts has produced Mr. Harrifon’s 
valuable time-keeper ; and from the firft balances, 
which were either too heavy, or too light, we have 
attained to thofe fcales of Mr. Matthey * as eafily 
turned as they are accurate. What however is 
ftill more aftonifhing is, that, notwitbftanding the 
importance of having fixt meafures for the aiinen- 
fions of bodies, we have not as yet ufed any in 
praCtice, but fuch as muft be modeled immediately 
from others. 
It is true, that in the conftrudion of an Hygrome- 
ter, I was affifted by the general notions of regularity, 
gathered from the conftruCtion of other meafures 
of the fame kind ; and of courfe my hygrometer 
is much forwarder in this refpeCl than the ther- 
mometer, for inftance, was in its origin. 1 there- 
fore only compare the difficulties peculiar to the hy- 
* An excellent mechanic, whole death is a lofs to a king, 
who knows the value ol men of merit. He was a native of 
Vale-Orbe, in the Pays de Vaud, and in the fervice of his Sardi- 
nian Majelly j and has written a Treatife on Balances , which 
ferves as a law to all the fcale makers in the dominions of that 
prince. 
grometer, 
