28 PROCEEDINGS OF THE AMERICAN ACADEMY 



July 11 to 20. This peculiar period of ten days almost free from 

 storms is oue of the most marked features of the summer. There 

 were no reports on the 11th, 12th, or 13th, duriug the passage of an 

 area of high pressure, and the approach of two low pressure centres 

 which passed north and south of New England on the 14th. The 

 northern of these cyclonic centres ran down the St. Lawrence valley, 

 on a path seemingly well adapted to giving us local storms ; but the 

 other one moved northeastward from New Jersey, probably along the 

 southern coast of New England, and controlled our weather, giving us 

 a light general rain, with easterly or southeasterly winds and a low 

 temperature (mean max. 69°). A few reports of moderate thun- 

 der came from Rhode Island in the evening. On the 15th, the tem- 

 peratui-e rose, but there were no reports. The 16th brought an area 

 of high pressure along the Atlantic coast, with still rising tempera- 

 ture (mean max. 83°) ; a few sharp local storms were here developed, 

 the most severe being in central New Hampshire at 15*^, where the 

 lightning struck in several places ; but reports were received from only 

 five observers. The absence of storms on the 17th is remarkable. 

 A low pressure centre had come fi-om the West to Lake Pluron, and 

 thence over Canada north of the St. Lawrence. It produced the hot- 

 test mean maximum temperature of the summer (92°), with the char- 

 acteristic circulation of winds that in other cases developed violent 

 storms ; and yet on this day there were only three reports, all of heat- 

 lightning in the evening. "We are led to suppose that the position of 

 the low pressure centre and the arrangement of winds proper to give 

 storms in New England was not reached until night, when the absence 

 of sunshine prevented their development. Still, it is surprising that 

 none came to us that had formed farther west in the daytime. 



The ISth, 19th, and 20th furnished no reports; they were charac- 

 terized by the passage of an area of high pressure, with fair, warm 

 weather. 



July 21. After this long period of inaction in New England, there 

 came a low pressure centre that had been loitering in Dakota on the 

 18th and 19th, and that moved rapidly eastward on the 20th. The 

 morning of the 21st found it north of Lake Huron, and at 15'* it was 

 in southwestern Maine : its progressive velocity was therefore about 

 60 miles an hour during this interval. Several storms accompanied this 

 low pressure area. Two of them are among the most interesting of 

 the summer, both being notable for their high velocity of 48 and 43 . 

 miles an hour, and their violent wind squall. They are described in 

 some detail on p. 45. The mean maximum temperature for the day 

 was 90°. 



