during the Quarter ending December 31, 1849. Ill 



average for the season ; its mean daily excess was 6°*3. From 

 December 5 to 8 the mean daily excess of temperature was 4°, 

 and between December J 4 and 19 the average excess was 

 6°'9. This warm period of six days was remarkable, as oc- 

 curring between two very cold periods. The temperature in 

 December was variable; on the 15th day it exceeded the 

 average by 13°'4, and on the 28th it was 13° below. 



The mean temperature of the air at Greenwich for the three 

 months ending November, constituting the three autumnal 

 months, was 51°*3; and that of the average from the seventy- 

 nine preceding autumns was 49°*3. 



For the month of October was 51°'l, exceeding the average 

 of the seventy-nine preceding years by 1°'8, and that of the 

 preceding eight years by 1°*5. 



For the month of November was 44°* 1, exceeding the ave- 

 rage of the seventy-nine preceding years by 1°*7, and less 

 than that of the preceding eight years by 0°*4. 



For the month of December was 39°*1, exceeding that of 

 the average of the preceding seventy-nine years by 0°*3, and 

 being less than the average of the preceding eight years by 1°*3. 



The mean for the quarter was 44°* 8, exceeding the average 

 of seventy-nine years by 1°'3, and being of the same value as 

 that of the preceding eight years. 



The mean temperature of evaporation at Greenwich — 



For the month of October was 48°'2 ; for the month of 

 November was 42°*2 ; and for the month of December was 

 37^-9. These values are 0°'8, 0°-9, and l°-3 below those of 

 the averages of the same months respectively in the preceding 

 eight years. 



The mean temperature of the dew-point at Gree?iwich — 



For the months of October, November and December, were 

 45°-l, 39°-8 and 35°-l respectively. These values are \°0, 

 1°*7 and 2°* I below respectively the averages of the same 

 months in the preceding eight years. The mean value for the 

 quarter was 40°*0, and that of the preceding eight years was 

 41°*6. The difference of these numbers shows that the air 

 has been less humid than usual. 



The mean elasticforce of vapour at Greenwich for the quarter 

 was 0*267 inch, being /«5 than the average from the preceding 

 eight years by 0'017 inch. 



The mean weight of water in a cubic foot of air for the 

 quarter was 3*1 grains, being of the same value as that of the 

 average from the eight preceding years. 



The mean additional weight of water required to saturate a 

 cubic foot of air was 0*5 grain.. The average from the eight 

 preceding years was 0*4 grain. 



