I7lr 



njulatlon of heat around our bodies, by its impulfe and rapid 



fucceffion, both cooling our clothes fafter, and carrying away 



the warm air that was Intangled in them. The Doctor (ays, that agitation of 



"the fenfationcf coldnefs, therefore, produced by wind, o"" J^^ ^eatS* 



agitated air, is fo much ftronger than that produced by equally, bodies, does 



cold air in a Hagnaling ftate, that we are often perfiiaded the not render the 



" " ' air colder, 



agitated air is adlually colder, until we examine it by the 



Iher.iTiometer ; and Dr. Boerhaave thought the deception fo 

 i^rong, that he conliived an experiment to remove it com- 

 pletely (Boerhaave Elementa Cheraire.) He fufpended a 

 thermometer in the air of a large room for fome time, and 

 noting the degree to which it pointed, he then directed againft 

 the bulb of it a ftream of air impelled by a large bellows in 

 the lame room;— that ftream of air wogld certainly feel to a 

 perfon who oppofed any part of his body to it, conGderably 

 colder than the reft; of the air in the fame room ; but the ther~ 

 mometer is not in the leufi uffeRcd by it. And it would be eafy nor hotter, 

 to exhibit another experiment to fliew, that agitated air is ^^""^h it mekq 

 not made colder by agitation. A piece of ice, for example, 

 being fufpended in the air of a warm room, and blown upon 

 by bellows, inflead of being thereby kept the more cool, as 

 our hand would be, and preferved the longer from being 

 totally melted, would certainly be melted fo much the fafter, 

 than when the air is allowed to ftagnate in fome meafure 

 siround it." 



I take the liberty of troubling you with this In confequence M. Wintfr 

 of a communication from vour ingenious correfpondent, J^""" , ^ ,,^ *"" 



•' . ' trom beUows 



Mr. Richard Winter, publiPied in the lati Number of your gave outheat. 

 excellent Journal, where liis experiment on the elTed pro- 

 duced on a thermometer by a blaft of air from a pair of 

 bellows, direftlv contradids Dr. Black's aflertion, that " th^ 

 tlierniometer is not in the leaft affected by it." 



That there is great truth in Dr. Black's general ftafement Queftions re- 

 of the fedi. cf a blaft of air cooling a body warmer than it- JP^'"S t^efe 

 felf, by atrording a continued fcries of frefti furfaces to carry 

 90" the caloric, 1 have no doubt, and that it ftiould have an 

 equal effect in warming a body colder than itfelf, feeijis 

 equally evident, or by fupplying the colder body with caloric. 

 B.ut in the cafe of the thermometer being raifed four degrees, 

 (3s ftated in, Mr. Winter's experiments) we arc not told that 

 it was oi^ a temperature lower than that of the air of the 



roora 



