114 Proceedings of the Association 
as well as light therefore show that the theory of undulation is 
not an imagination, but the expression of a daw. The minimum 
of heat, as proved by his experiments with the thermo-electric 
pile, does not correspond with the minimum of light. Among 
ames, there are many which give but little light, but which 
give great heat; as, for example, the flame of hydrogen. The 
amount of radiant heat and radiant light were found to be about 
the same. 
The spots on the sun are colder than the surrounding surface ; 
and its surface is variously heated. This result he obtained by 
avery simple experiment of throwing the disc of the sun on a 
screen, and placing the very sensitive “thermo-electric pile before 
its different parts. He had not yet concluded his experiments on 
the sun, and had not measured the comparative heating powers 
of the centre and circumference, from which results very impor- 
tant consequences would be drawn. 
This apparatus he fitted to a common pasteboard tube, covered 
with ua paper externally, and blackened internally, with which 
he red the heat of distant objects. He could detect the 
heat of a man’s face a mile off; that of a house, five miles off. 
He thus discovered that the coldest spot of the sky is at the zenith. 
One day, on directing his tube to a cloud, from which flashes of 
lightning proceeded, he was astonished to find it indicated a great 
degree of cold ; he afterwards found out that a considerable quan- 
tity of hail had fallen from this cloud. 
- He was not satisfied with the appearances of heat supposed to 
have been derived from the moon. The heat that other observ- 
ers have got, is probably the reflected heat of the sun, and not 
the moon’s proper heat 
12. On the Absorption of Carbonic Acid by Water, Saline 
Solutions, and various other liquids ; by Prof. W. B. Rocers and 
Prof. R. E. Rocers.—In an oral abstract of this paper, Prof. W. 
B. Rogers stated that the researches to which it referred had been 
entered upon nearly a year ago by himself and Prof. R. E. Rogers, 
according to the methods employed by Dalton and Saussure, but 
from the irregularity of the results incident as they found to these 
modes of operating, they were led to relinquish them after much 
unsatisfactory labor. In the more perfect process, afterwards 
adopted, the determinations were uniform and consistent, seldom 
giving a variation in successive trials of one per cent. The ap- 
paratus employed, of which a figure was exhibited to the Associ- 
ation, is so constructed as by a peculiar connection to enable the 
operator to agitate the liquid with the gas while the tension re- 
mains unaltered. ‘The absorption is measured by a column of 
mercury in a fixed tube of syphon form, connected with the 
in which the agitation is given by a vibrating motion. ‘The 
See ieieacin g tube, as well as the gasometer ying the 
—: 
0 Ri iia ioe 
