C 438 ] 
in my hygrometers, I think it reasonable to hope 
that this instrument will receive a fenfible degree of 
perfection on a Second trial ; and that in time it will 
be brought to a Sufficient degree of accuracy. It is 
true there are Some difficulties in the way of this : 
but have we riot Sufficient motives for endeavouring 
to overcome them ? The air we breathe, and that 
which Surrounds us ; the places we inhabit, and 
thofe which Serve either to enclofe or to preferve 
So many different bodies intended for our Several oc- 
casions, are all of them more or lefs filled with that 
SubStance, differently modified, to which I have given 
the name of humor. It alfo produces very fenfible 
effeCts in them ; Some of which very properly excite 
our curiofity, others may be turned to our advan- 
tage, and many of them effentially affect our health. 
It is therefore of great confequence to natural philo- 
sophy in general, and to oeconomy, and medicine, in 
particular, that we Should obtain a meafure by which 
we may, with Some degree of certainty, eftimate the 
local and aCfcual qualities of this SubStance, and by 
this means forefee its effeCts ; which for the gene- 
rality we only become acquainted with after they are 
produced. Thefe Sciences are not perhaps lefs con- 
cerned that we Should difcover the nature itfelf of 
this agent, and the different manners in which it ope- 
rates : the knowledge of which may enable us to 
avail ourfelves of reafon in the investigation of cer- 
tain effeCts, which, without fuch helps, might efcape 
our obfervation. As thefe are the feveral ufes of an 
exaft hygrometer, we may readily perceive how 
many new tracks fuch an instrument may open to 
us, in our investigations of nature, which however 
2 we 
