■t 526 1 
to afcertain the degree of cold, which we may have 
had, higher than that time. 
The near agreement between your regifter and 
mine is remarkable, at noon and night, when the ob- 
fervations were made at the fame hour. The con- 
fiderable difference, on the y h inftant, a. m. when 
your thermometer was 6 deg. higher, I attribute, 
partly, to your obfervation being made an hour later 
than mine, and after the fun had been above the ho- 
rizon three-quarters of an hour: For I have found, 
by long obfervation, that the coldefl time of the day, 
in general, is between an hour, and half an hour, be- 
fore the fun rifes. But, perhaps, this difference may 
likewife have been occafioned, in part, by warm fleams 
tranfpiring the earth, at that time ; for I have feveral 
times obferved our fudden thaws, this winter, to have 
been attended with circumftances, which led me to 
think they had their rife from fuch a cauie. Some 
mornings, in a great froft, have been univerfally clear 
before day; when, having regiftered the ftation of 
the mercury, I afterwards frequently viewed the ther- 
mometer, and found it to rife 3, 4, or more, deg. 
when another, which I always regifter with it, and is 
on the fame fide of the houfe, but at a window of a 
room one ftory higher, has not rifen at all. From 
whence I expected a thaw, and never have been de- 
ceived. It has, in an hour’s time, grown cloudy, and 
the thaw vifible, and this before fun- riling, and with- 
out any change in the wind ; which maketh it pro- 
bable, it muft have been caufed by a fubterranean 
heat, palling thro’ the furface of the ground. 
I beg leave to make one obfervation more, which 
is, that the air in my chamber, which is moflly fliut 
up. 
