487 
THERMOMETRY. 
*Ot 
O F the various philosophical instruments which are met 
with in the hands of that remarkable body e< the general 
public," it may certainly be said that none is so widely known 
as the Thermometer ; perhaps widely disseminated would be 
a preferable expression, for it may be doubted whether one 
in ten of those who use these instruments know anything about 
their theory or practical nature. 
Meteorology as a science has made great strides during the 
last few years ; that it has substantial claims on our attention 
for sanitary reasons is now pretty generally conceded, and 
that the weather has much to do with the public health few 
will now be found bold enough to deny. Under these cir- 
cumstances it does not seem unappropriate to call the attention 
of the readers of the Popular Science Review to it ; and of 
its practical branches few are more interesting than that 
relating to the measurement of temperatures, which will form 
the subject of the present paper. 
Any discussion as to the physical character of heat, as to its 
general relations, would be not only beside the object we 
have now in view, but would require a whole volume for 
its due consideration. We must be content to take heat 
as we find it, and see how it can be approached so as 
to deduce facts calculated to be of a useful character. 
We can obtain crude ideas in reference to it in a variety 
of ways. For philosophical purposes, the expansion it uni- 
versally causes in all natural substances affords an easy and 
convenient method of estimating it in a relative sense. Every- 
body knows by experience that a pair of boots which are a 
perfect fit in the month of January, if get-on-able in July, 
can only be worn with greater or less inconvenience and 
discomfort. Why ? The reason simply is, that the natural 
heat of the summer season causes an increase in the 
bulk of the foot, and this can only be accommodated by 
an enlarged boot, except the wearer make up his mind to 
endure torture for fashion's sake, as many in fact do. 
Another familiar effect of heat is well known to the laundress. 
Her “ box-iron " has its heater made much smaller than the 
case, in order that the former, when made red-hot to subserve 
