508 Mr. J. Glaisher's Remarks on the Weather 



5°*0 above those of the years 1844' to 1847 respectively; or it 

 is 2'^'2 above the average value for these six years. 



The mean value for the quarter was 36°'3, which is 1°1 

 above the average for the six preceding years. 



The meafi xveight of 'water in a cubic foot of air for the 

 quarter was 2*7 grains, which is of the same value as that of 

 the average for the six preceding years. 



The additional iveight o/'watcr required to saturate a cubic 

 foot of air was O'i? grain ; the average for the six preceding 

 years was 0*36 grain. 



The mean degree of humidity of the atmosphere for January 

 was 0'837, for February was 0-864, and for March was 0*839; 

 these values being less than the average for the six preceding 

 years by 0*077, 0'029, and 0'002 respectively; the value for 

 the quarter was 0"846, which is 0*036 less than the average 

 for these years. 



77/1? mean elastic force of vapour for the quarter was 0*230 

 inch, which is 0*006 inch above the average for the six pre- 

 ceding years. 



The mean reading of the barometer at Greenwich for 

 January was 29*816 inches, for February was 29*517 inches, 

 and for March was 29*505 inches ; these values are 0*057 inch 

 above, 0*199 inch beloiv, and 0*256 inch bcloxv respectively, the 

 averages for the seven preceding years. The mean value for 

 the quarter was 29*613 inches, which is 0*132 inch l)clow the 

 average for these years. The readings of the barometer 

 during the greater part of the quarter were remarkable, and 

 will be spoken of presently. 



The average weight of a cubic foot of air nnder the average 

 temperature, humidity and pressure, was 545 grains; the ave- 

 rage for the six preceding years was 549 grains. 



The rain fallen at Greenwich in January was 1*2 inch ; 

 in February was 2*6 inches; and in March was 3*1 inches; 

 the average values for the seven preceding years were 

 1*9 inch, 1*6 inch, and 1*4 inch respectively. The total 

 amount fallen in the quarter was 7'9 inches, which is 3*0 

 inches greater than the average for the years 1841 to 1847. 

 I shall presently speak of this large amount of rain. 



The temperature of the Thames water was 39°*3 by day, and 

 37°*0 by night. The water, on an avertige, was 2°*4 wariner 

 than the air. 



The horizontal movement of the air was about 168 miles 

 daily, being somewhat more than its average value. 



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 

 71°-5 and 15°-8. 



