240 



Meteorology of New JTaven. 



Taking the average of the dates and temperatures for the two 

 series of years before and after 1820, we obtain the following results • 



These numbers agree perhaps as well as could be expected upon 

 the supposition that no permanent change of climate has occurred. 



Another phenomenon which affords a standard for comparing dif- 

 ferent climates, is the time of occurrence of the first and last appear- 

 ance of snow during the winter season. We have therefore made a 

 careful comparison of all the meteorological journals, and have deter- 

 mined as accurately as possible the dates of these phenomena, together 

 with the depth of the snow. The results are shown in the following 

 table. Column 2d gives the date of the last snow in the spring of 

 the year, the snow being sufficient in quantity to be measured, or to 

 whiten the surface of the ground. Column 3d contains the date of 

 the last recorded appearance of snow in quantities too small to be 

 measured, being generally designated by ' a snow squall,' or ' a few 

 flakes of snow.' Columns 4 and 5 contain similar information respect- 

 ing the first appearance of snow in the autumn. 



