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 
er 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 aslight 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 ont 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 
eee pnerieal 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 
