104 PHILOSOPHY OF STORMS. 



In this storm then, as in the nine investigated before, the 

 wind blew towards the centre, and consequently upwards 

 in the middle and outwards above at least in Massachu- 

 setts. Mr. Daniel C. Sanders, of Medfield, seventeen miles 

 south west of Boston, says : "often there were three strata 

 of clouds, the upper one very high, moving from the west, 

 nearly opposite to the lower stratum. The middle one 

 was very changeable in its direction." 



And also at Bennington, Vermont, Mr. Jonathan Hunt 

 says ; " In almost all violent storms from the east, there is 

 an upper current from the west." 



There is therefore the strongest reason to believe that 

 rain is caused by the cooling produced by the rarefac- 

 tion of the air in its upward motion in the centre of the 

 storm. 



112. The storm which commenced on the night of the 

 19th June, is not less remarkable than the one just describ- 

 ed. It seems also to have travelled south or south west, 

 for on the night of the 19th, and the next day, the rain was 

 greatest at Silver Lake, in the northern part of Pennsylva- 

 nia, and on the night of the 20th, and the next day, it was 

 greatest at Baltimore, and it did not reach Hawsburg, Rap- 

 pahannock county, Va., till the 21st, when it rained very 

 heavily, the wind having veered round to the north east. 

 At Staunton, Va., it was clear all day the 21st and 22d, till 

 evening, and the north east storm did not set in till the 

 24th. 



In the wood cut we have given the direction of the wind 

 by means of arrows at all the places from which we have 

 any accounts. On the 20th of June, there fell nearly three 

 inches of rain, including that of the preceding night, at 

 Silver Lake. Much more rain fell here than at any of the 

 surrounding places of observation. There was but little at 

 Foxburg, Gettysburg, and Harrisburg, and it did not 

 commence at Baltimore till half past seven o'clock, P. M., 



