E. Loomis — Contributions to Meteorology. 247 



This change in the amount of rain-fall adopted as the standard 

 was rendered necessary by the gradually increased number of 

 the stations of observation. 



The number of cases of rain-fall which fulfilled the preced- 

 ing conditions was 106. The geographical extent of some of 

 these rain areas was remarkable. In ten cases the area of one 

 inch rain fall was at least 500 English miles in length; and in 

 three cases it exceeded 700 miles in length. Frequently the 

 entire rain-area is an oval figure whose length exceeds 1000 

 miles, and whose breadth exceeds 500 miles. 



These 106 cases were distributed by seasons as follows : 

 Winter, 30 cases ; Spring, 19 ; Summer, 15 ; and Autumn, 42. 

 These great rain areas are thus seen to be most frequent in 

 Autumn, and the month of greatest frequency is November. 

 We have found that excessive rains at single stations are most 

 common from July to September. 



6. The directions of the station of greatest rain-fall from the 

 point of minimum pressure were as follows : 



Rain center in the S.E. quadrant, 40 per cent of the whole number. 



N.E. " 37 



S.W. " 10 



N.W. " 3 



Direction nearly South, 4 " 



East, 5 



North, 1 



We see that the greatest rain-fall generally occurred on that 

 side of the center of low pressure towards which the low area 

 was advancing ; that is, the low center moved towards the rain 

 area. In about 60 per cent of the whole number of cases, these 

 two directions were inclined to each other less than 60°. This 

 coincidence would have been more frequent, if the direction of 

 progress of the low centre had been compared with the direc- 

 tion of the greatest rain area, instead of the station of greatest 

 rain-fall ; for frequently the station of greatest rain-fall was 

 not included in the greatest rain area. In several of the cases 

 in which the principal rain center was on the west side of the 

 low center, the geographical extent of the rain areas on the east 

 side was greater than that on the west side. This fact seems 

 to indicate that the general movement of the winds depends 

 more upon the geographical extent of the rain areas, than upon 

 the quantity of rain which falls at a single station. In two 

 cases when the rain center was in the northwest quadrant, the 

 center of least pressure moved towards the northwest, which 

 appears to indicate very distinctly the tendency of a low center 

 to incline towards a rain area. When the station of greatest 

 rain-fall was southwest of the center of minimum pressure, the 

 rain-fall on the southwest side accompanied the advance of an 

 area of high pressure, with winds from the northwest quarter 



