1868.] 



527 



[Cha,se. 



This formula appeared td give snflficient weight to any possi- 

 ble shifting of lunar influence, by prevailing winds or other 

 occasional disturbances. 



For greater symmetry and simplicity the normal lunar month 

 was assumed to consist of thirty days, the 30th day (moon's 

 age 29) being computed by the formula 



^29= ( ^28 + 4y,8',^ + j/o) -^4 



The solar hourly barometric curve was constructed from the 

 values given in Guyot's tables (Bache); all the others, from the 

 results of original computation. 



TABLE VI. 



Number and amount of Heavrj Rains (1 inch or more) at 

 Philadelphia^ on different days of the Lunar Month. 



The data for determining the Philadelphia hourl}' rains are 

 not so satisfactory as those for the dail}^ rains. A self-register- 

 ing gauge was kept at Girard College, but the oft-repeated mar- 

 VOL. X. — 3t 



