223 
influence in the solar rays. 
an increment of temperature of i°, between 62.05 and 77.65, 
would be .000586, from which the foregoing result does not 
differ greatly. 
If we estimate the change of intensity by the difference in 
the times of vibration, calling the intensity at the temperature 
6o°, 1 ; we shall have, 
Intensity at temperature 84° = z = .992462. 
We have therefore here a decrease of intensity .007538, in 
consequence of an increase of 24 0 in temperature ; or a decre- 
ment .000314 corresponding to an increment i° in tempera- 
ture, between the temperatures 60° and 84 0 . This is consi- 
derably less than was deduced from the deviation due to tor- 
sion, which arises in some measure from the acceleration 
from torsion being very nearly constant at different tempera- 
tures, and therefore tending to diminish the difference in the 
times of vibration. 
The following observations were made between n h 30" 
and i2 h 4o m of the 10th of June, 1825, under very favourable 
circumstances, the sun shining clear and strong the whole 
time. The heavy needle employed in the last observations 
was again made use of ; it now rested on the pivot. The 
point where the vibrations commenced for each 40 vibrations 
was 90° from zero. 
