North America hy Dr Holyoke and Professor Dewey. 856 
degree of the true mean, deduced from 24 observations ; and 
hence we are led to a conclusion, which we consider as of very 
great importance in meteorology, that the mean two observa- 
tions at 10^ A.M. and 10^ P.M. is not only nearer than any two 
observations to the mean of the maximum and minimum, as Mr 
Gordon found it to he ; hut that it is nearer than the mean of 
the MAXIMUM and minimum themselves to the true temperature 
of the day^ and even nearer than the mean of any three obser- 
vations. 
If these remarks should ever meet the eye of Professor 
Dewey, we trust he will adopt the observations of 10^ A. M. and 
10^ P. M., as not only saving the trouble of 865 observations 
in the year, but as giving the most correct mean result. 
As it would be desirable to possess a series of observations 
made in Scotland for every hour of the day, for a small number 
of days, we beg leave earnestly to suggest such a series of 
experiments to some of those active meteorologists who have 
undertaken to keep regular registers of the thermometer in 
Scotland. 
D. B. 
Art. XIX. — Account of Natural Ice-Houses in Connecticut. 
By Benjamin Silliman, Professor of Mineralogy in Yale 
College 
That ice is perpetual in some climates is notorious. That 
it is so even in those of the Torrid Zone, upon mountains which 
rise to the height of three miles, is also well known. It is, how* 
ever, a rare occurrence, even in cold climates, that ice is perennial 
on ground which possesses no more than the common elevation. 
An instance of this kind has, however, recently come to our 
knowledge. It exists in the State of Connecticut, in the town- 
ship of Meriden, mid- way between Hartford and Newhaven. 
This natural ice-house is situated in about 42° of north latitude, 
From American Jonrnal of Science vcl. iv. p. 174. 
