FROM THE HIGHER ATMOSPHERE. 493 
millesimal degrees. But, in the same situation, the common z- 
thrioscope might, be expected to mark an impression of cold 
from above, as just so much diminished. No opportunity, 
however, has yet occurred, on a large scale, for making these 
interesting observations. The ascent of a balloon would afford 
the readiest mode of verifying and extending the theory. | 
. The nature and intensity of the cold and hot pulses excited 
in the several strata of the atmosphere, may be easily under- 
stood from (fig. 9. Pl. XI.) Let two equal and opposite 
circles touch the straight line AB, which divides a stratum 
of cold, from another of warm, air.. While the opposite dia- 
meters CD and Cd represent the forces of the perpendicular 
pulses of cold darted downwards, and of heat shot upwards, the 
chords CE, CF, CG, and CH, and Ce, Cf, Cg, and Ch, will 
likewise exhibit the strength of the Pulees which are transmit- 
ted with various obliquity. 
- The:inverted zthrioscope likewise disiayews the quality and 
measure of the pulses projected from the ground. These, in 
general, are: very feeble, seldom in this:climate exceeding three 
or four degrees. In the progress of a bright day, as the ground 
grows warmer than the incumbent air, it excites hot pulses ; 
but, as the sun declines, the effect gradually diminishes ; 
till this again returns, increasing with a contrary character, 
when the surface of the earth has become relatively colder. 
The same instrument being suspended a few feet above the 
ground while the sky appeared clear and blue, a silver tray 
was laid upon it, and the reflected impression of cold amount- 
ed to 25 degrees ; but, on interposing a plate of glass, it was re- 
duced to two degrees; and on removing this, and pouring a 
sheet of water over the silver, the effect was absolutely extin- 
guished. The absorbent influence of water, and consequently 
of clouds, was thus distinctly shown. 
The 
