FROM THE HIGHER ATMOSPHERE. 49S 



millesimal degrees. But, in the same situation, the common se- 

 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. PI. XL) 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, C/, Cg, and Ch, will 

 likewise exhibit the strength of the pulses which are transmit- 

 ted with various obliquity. 



The inverted aethrioscope likewise discovers 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 pourino- 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 



