AT NIGHT, FROM THE EARTH, ETC. 
145 
From the preceding tables we learn the following particulars : — Tables I. to VI., 
XVII. to XX., and XXIX. to XXXII. contain the results of observations when the 
excess of air-temperature above that of long grass was less than 5°; such observa- 
tions having been taken at times when the sky was wholly covered with cirro- 
stratus cloud, after having been cloudless, during which state a series of observations 
had been taken. By examining the last column of these Tables, it will be seen that 
when the excess of air-temperature above that of long grass has amounted to 4° or 5°, 
the clouds have been noted as being high, and when t he excess was less than 3°, they 
have been mentioned as being low, or no mention has been made as to their height. 
Tables VII. to X., XXI. to XXIV., and XXXIII. to XXXVI. contain the results of 
observations at times when the excess amounted to 5°, 6°, 7 °, or 8°; and from the last 
columns in those tables, it appears that at such times the sky was frequently cloudy, 
and when wholly so, that the clouds were high ; that the air was in frequent motion, 
and at times the wind was blowing with a pressure of 4 lbs. on the square foot; that 
the atmosphere was occasionally thick by haze or vapour, and that dew was seldom 
deposited. Tables XI. to XIV., XXV. to XXVII., XXXVII. to XL. contain the 
results of the observations at times when the excess was 9°, 1 1°, or 12°; and at those 
times the sky has been generally clear, the air calm, and the atmosphere frequently 
hazy, misty, or vapour or fog was prevalent. Dew was also frequently deposited ; 
in two cases contained in Tables XI. and XXXVII. occurring 1843, Nov. 12 d 13 h 5 m , 
and in 1844, Feb. 20 d 5 h , the sky was wholly covered by high and thin clouds. 
Tables XV. and XVI., XXVIII., XLI. and XLII., exhibit the results when the ex- 
cess was 13° and 14°, and at those times the sky was generally clear, and the air was 
calm ; haze and vapour were occasionally prevalent. Tables XLIII. and XLIV. con- 
tain the results when the air-temperature exceeded that of long grass by quantities 
varying from 15° to 19° ; and by examining the last column of these Tables, it appears 
that at those times the sky was cloudless and bright, the atmosphere was clear 
without haze, mist or vapour, and a perfect calm prevailed. 
From the above particulars it appears that at times when the sky was entirely 
covered with low cirrostratus clouds, the readings of a thermometer placed on long 
grass was the same as that in the air; that with the same clouds at a moderate ele- 
vation, the reading of the thermometer in air has exceeded that on long grass by 3°; 
and on those clouds being high, this excess has amounted frequently to 5°; and if 
other clouds than cirrostratus covered the whole sky this excess has been as large as 
10°. At times when the sky has been free from clouds but not bright, haze and 
vapour being prevalent, the above excess has amounted to 10°, 11°, or 12°; and at 
times when the sky has been both bright and clear, with the air calm, no mist, haze, 
vapour or fog being prevalent, this difference has frequently amounted to 14°, less 
frequently to 19°, and sometimes to 20°. 
In Tables XLII. to XLIV. are exhibited the great excess of the reading of a ther- 
mometer in air above those of thermometers placed on substances whose power for 
MDCCCXLVII. 
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