132 Mr. J. Glaisher's Remarks o?i the Weather 



inch, which is O'OSO inch above that for the average of the six 

 preceding years. 



The mean reading of the barometer at Greenwich for the 

 quarter was 29829 inches, which is O'lll inch above thaX. iov 

 the six preceding years. 



The average "weight of a cubic foot of air under the average 

 temperature, humidity and pressure, was 540 grains; the 

 average for the six preceding years was 543 grains. 



The rain fallen at Greenwicii within the quarter was six 

 inches in depth ; this quantity is two inches less than the 

 average for the six preceding years. The total amount of 

 rain fallen in the year 1847 was 17'6 inches, which is nearly 

 eight inches less than the average amount for the six preceding 

 years. 



The temperature of the Thames "water was 48°'2 by day, and 

 47°'6 by night. The water on an average was nearly of the 

 same temperature as the air. 



TJie horizontal movement of the air was about 950 miles 

 weekly, being somewhat less than the average amount. 



The highest and lowest readings of the thermometer in air at 

 the height of four feet above the ground, and protected as 

 much as possible from the effects of radiation and rain, were 

 73°-2 and 24°'5. 



The average daily range of the readings of thermometers 

 in air at the height of four feet was 1 1°*7, which is 3°*8 greater 

 than the average range from the six preceding years. 



In October the reading of the thermometer on grass was at 

 or below 32° on five nights, and the lowest reading was 26°"5. 

 In November it was below 32° on thirteen nights, and the low- 

 est reading was 18°. In December it was below 32' on six- 

 teen nights, and the lowest reading was 19°- 3. The periods 

 of time, however, during which these readings have continued 

 have been very short, owing to the very cloudy state of the 

 sky during the nights. The amount of heat radiated from the 

 earth at night during the past quarter has been very small 

 indeed. 



The mean amount of cloud during the quarter was such as 

 to cover upon the average a little more than three-fourths of 

 the whole sky. Tiie month of December was more clouded 

 than any month since Januarj' 18+5. 



It is a fact well worthy of notice, that from the beginning 

 of this quarter till the 20th of December, the electricity of the 

 atmosphere was almost always in a neutral state; so that no 

 signs of electricity whatever were shown for several days 

 together by any of the electrical instruments. During tliis 

 period, I myself several times minutely examined the whole 



