INTRODUCTIOK. JIJ 



Aeat of fprings near Edinburgh, feems to be 47; 

 and London, 51. Phil. Tranf. vol. Ixv. From the 

 Meteorological Journals of the Royal Society, pub- 

 llfhed in the Philofophical Tranfadions, it appears 

 that the mean heights of the thermometer, kept with- 

 put and within the houfe, are as below : 



For 



And, therefore, according to thefe obfervations, 

 the metn heat of four years, eftimated by the exter- 

 nal thermometer, is 51. The lead height, during 

 this period, was on the 31ft of January 1776, at eight 

 o'clock in the morning, when it was 13: And 

 thegreateft height, which was on the 13th and 14th 

 of July 1778, at two in the afternoon, was 86. 



It is well known that heat, in all bodies, has a 

 tendency to difFufe itfelf equally through every part 

 of them, till they become of the fame temperature : 

 Again, bodies of a large mafs are both cooled and 

 heated ilowly. Befides the mafs of matter, there are 

 two other confiderations of much importance, in the 

 flow or quick tranfmiffion of heat through bodies : 

 Thefe are, their difterent conducing powers, and 

 their being in a ftate of folidity or fluidity. The 

 conduding powers of heat are well known to be 

 very various in different bodies ; nor are they hitherto 

 reducible to any law, depending either upon the 

 ^enfity or chemical properties of mattep; 



B 4 Metals 



