IV. — On Improvement in Meteorological Registration. 
By Mr. Tuomas Hopkins. 
Read January 12th, 1858. 
Great numbers of persons are engaged in collecting in- 
formation respecting the changes which, it is well known, 
frequently take place in our atmosphere. Many indivi- 
duals register the alterations indicated by meteorological 
instruments with great care and industry, and govern- 
ments have established and maintained observatories for 
this purpose, at considerable cost; yet it has been said 
by eminent men, of whose competency to form opinions 
on the subject no doubt can exist, that the results obtained 
are of little value. This suggests the idea, that the course 
pursued in investigating the subject may be defective, and 
warrauts a particular examination of the methods adopted. 
The weight of the atmosphere, in each locality, is almost 
constantly varying, and the amount of that weight as 
well as the alterations which it undergoes are indicated by 
the barometer. But the most vigilant watching of the 
height of the mercury, combined with observations of 
the state of the sky, has failed to exhibit to our view the 
causes of the fluctuations of atmospheric pressure. There 
is a general impression that, in some way, heat lightens 
the atmosphere, and that cold makes it heavy, but in what 
way the changes, from the one to the other state, are 
effected, is not known. 
