83 



very sudden and great. The mercury in Farenheit's 

 thermometer has been known to descend from 92^ to 

 47^ in thirteen hours. 



It is taken for granted, that the preceding table of 

 average heat will not give a false idea on this subject, 

 as it proposes to state only the ordinary heat and cold 

 of each month, and not those which are extraordinary. 

 At Williamsburgh in August 3766, the mercury in 

 Farenheit's thermometer was at 98° corresponding with 

 29i of Reaumur. At the same place in January 1780, 

 it was 6° corresponding with 11^ below 0, of Reaumur. 

 I believe* these may be considered to be nearly the 

 extremes of Iieat and cold in that part of the country. 

 The latter may most certainly, as at that time, York 

 river, at York town, was frozen over, so that people 

 walked across it; a circumstance which proves it to 

 have been colder than the winter of 1740, 1741, usually 

 called the cold winter, when York river did not freeze 

 over at that place. In the same season of 1780, Chesa- 

 peake bay was solid, from its head to the mouth of 

 Patowmac. At Annapolis, where it is 5^ miles over 

 between the nearest points of land, the ice was from 5 

 to 7 inches thick quite across, so that loaded carriages 

 went over on it. Those, our extremes of heat and cold, 

 of 6° and 98° were indeed very distressing to us, and 

 were thought to put the extent of the human constitu- 

 tion to consideraljle trial. Yet a Siberian would have 

 considered them as scarcely a sensible variation. At 

 Jenniseitz in that country, in latitude 58° 27' we are 

 told, that the cold in 1735 sunk the mercury by Faren- 

 heit's scale to 126° below nothing; and the inhabitants 

 of the same country use stove rooms two or three times 

 a week, in which they stay two hours at a time, the 

 atmosphere of which raises the mercury to 135° above 

 nothing. Late experiments show that the human body 



* At Paris, in 1753, the mercury in Reaumur's thermometer 

 was at 30 1-2 above 0, and in 1776, it whs at 16 below 0. The 

 extremities of heat auH cold therefore at Paris, are greater than 

 at Williamsburgh, which is in the hottest part of Virginia. 



