FROM THE HIGHER ATMOSPHERE. 479 



other apparatus, into the country, for the greater convenience 

 of making observations. This pyroscope being let down with- 

 in a few inches of the ground, generally indicated an impres- 

 sion of heat during the day, seldom exceeding, however, three 

 or four millesimal degrees. But I remarked, with surprise, in 

 more than one instance, that towards evening, when the sky be- 

 came clearer, the liquor would fall a degree or two. Yet the 

 ground was still warmer than the air, and ought consequently to 

 have augmented, rather than diminished, the calorific pulsa- 

 tion. I now began to suspect that an opposite impression was 

 somehow showered from the atmosphere, and therefore set about 

 examining the subject closely; though a tract of cloudy and boi- 

 sterous weather greatly retarded my inquiries. I fitted, a little 

 below the sentient ball of an ordinary pyroscope, a small circu- 

 lar plate of tin, hammered into a slight concavity. The instru- 

 ment, having its action thus more than doubled, put the main 

 fact beyond all doubt. 



The object now was to discover, if those cold pulses shot 

 downwards from an azure sky, were subject to variation, and 

 whether they prevailed during the day, as well as at night. 

 I had a segment of a sphere hammered out of tin, about nine 

 inches wide, and three inches deep, with a vertical arch, to 

 which the pendant pyroscope was attached, the sentient ball 

 being placed in the middle between the centre and the 

 bottom. But the indications were not altogether satisfactory, 

 owing partly to the influence of strong light, though chiefly 

 to the disturbing effects of the violent winds which happened 

 then to prevail. I therefore resumed the erect pyroscope, and 

 augmented its action, by adapting under the sentient ball an 

 hemispherical tin-cup of about 2 inches in diameter. To screen 

 the instrument from the sun and the wind, I placed it in the 

 middle of a wide earthen pitcher set behind a north wall. The 



weather 



