AT NIGHT, FROM THE EARTH, ETC. 
193 
From Tables LI. to XCVII1. we learn the following- particulars. As the series of 
observations of the thermometer whose bulb was placed in the focus of the parabolic 
reflector extends over a much longer period of time than any of the others, it is 
desirable to discuss the results derived from it before consulting those deduced from 
the observations of the other instruments. Confining ourselves therefore to the 
numbers found from the observations of the thermometer in the reflector; first, to those 
in that division of every table under cloudy nights, it will be seen that during such 
nights its reading has frequently been higher than that in air, but it has generally 
been from 0° to 3° lower; frequently 4° ; less frequently from 5° to 8°, and occasion- 
ally 9° less than that in air. In Tables LXXII., LXXIV. and LXXV., quantities 
equal to 9° are exhibited ; and in the last-mentioned table there is one case of 13°*3 ; 
in Table XCI. there is one case of 1 1°*4 ; during the nights that these large differ- 
ences have occurred the clouds have been noted as being fleecy, thin and high. In 
Table LXXXV. large differences are exhibited ; the sky was noted at the time as 
being covered with cirrocumuli. 
As the results on those nights during which more or less cloud prevailed are gene- 
rally between those on cloudy and on cloudless nights, and nearly proportional to 
the amount of cloud ; the next division of these tables, which deserves particular 
attention, is that containing the results derived from cloudless nights. By examining 
the numbers in this division, it will be found that quantities less than 5° have taken 
place, even on cloudless nights. The atmosphere, however, on such nights has 
been noticed as being thick, and the air as being saturated with moisture. The fol- 
lowing is a list of these cases : — 
The result deduced from the observation 
taken in the year 
"1841, on March 10, at 21. 
1841, on March 29, at 21. 
1841, on June 20, at 21. 
1841, on July 9, at 21. 
1841, on September 6, at 21. 
1841, on November 19, at 21. 
1842, on April 8, at 21. 
1842, on August 3, at 21. 
1842, on August 16, at 21. 
1842, on August 17 , at 21. 
1842, on August 28, at 21. 
1842, on December 5, at 21. 
1843, on October 26, at 21. 
1843, on December 17, at 21. 
1844, on March 12, at 21. 
1844, on March 23, at 21. 
1844, on May 20, at 21. 
^1844, on June 16, at 21. 
2 c 
MDCCCXLVII. 
