on local Heat . 105 
The refuit entirely correfponded with what I had before ob- 
ferved refpe£Hng the no&urnal diminution of heat, and the 
particular ftate of the atmofphere requifite to produce it. The 
greateft variations which happened within the year were in 
O&ober and June; in the former month, the thermometers 
generally differed moft in the night; in the latter, moft in the 
day. From the 25th to the 28th of October, the heat below, 
in the night, exceeded, in a fmall degree, the heat above, at 
which time there was frequent rain, fometimes mingled with 
hail. From the Lith to the 14th, and alfo on the 31ft, there 
was no variation at all ; during which time likewife the wea- 
ther was rainy ; all the reft of the month proving clear, the 
air was found colder below than it was above, fometimes 9 or 
10 degrees. In the month of June, the greateft no&urnal 
variations happened from the nth to the 13th, and from the 
25th to the 30th ; at both which times there appeared to be 
two currents of wind, the upper current from the S.W., 
the lower from the N.E. *. On cloudy nights, the loweft 
thermometer fometimes fhewed the heat to be a degree or two 
warmer than the upper one ; but in the day time the heat 
below conftantly exceeded the heat above more than in the 
month of O&ober. See Tab. I. and II. f- 
Being 
* Sometimes thefe were rendered vifible by clouds in different flrata, moving 
in different dire&ions, and at other times by clouds moving in a contrary direction 
to a very fenfible current of air below. 
•f- The obfervations of the wind and weather were taken at Canterbury. In 
all the tables, the nocturnal degrees of cold belong to the night immediately 
preceding the day to the date of which they are placed. — With my thermometer 
I have fometimes fufpended hygrometers ; but their movement, although as con- 
formable as poffible to the moifture of the air, had not a fufficiently regular 
correfpondence with the variation of the thermometers to be inferted in the 
Vol. LXXVIJI. P Table < 
