[ 4^8 ] 



On the other hand, Mr. Prevoft, of Geneva, and of the Aca- 

 demy of Berlin, grounded on phyfical confiderations, namely, 

 that the fouthern winds incroach three degrees on the northern 

 fide of the equator, and that the north trade wind reaches no 

 farther than to the fifth degree, even on the north fide of the 

 equator, infers that the temperatures of the north and fouth feg- 

 ments, taken on thefe Twnits, are to each other inverfely as the 

 •fegments, and hence calculates the temperature of the north feg- 

 ment to be to that of the fouthern as 1 1 to 9- 38 Roz. Jour. 

 p, 369. He would have ftated this ratio * ftill higher, if he had 

 obferved, as Moore does in his -late excellent Treatife on Navi- 

 gation, that the northern trade wind extends only to the tenth 



degree 



* Some, I know, objefl that no ratio of heat can be juft, becaufe its firft origi- 

 nal degree cannot be found by obferi-ation ; but of what quantity can the abfolute 

 unit be rigoroudy found ? Muft we therefore difcard the units of weights and 

 meafure? The higheft degree of cold muft vary in various fubftances like fufi- 

 bility, for it muft be that, beyond which the attraflive power of their particles 

 ceafes, the refiftence' to a nearer approach being infinite ; now the force of this 

 power muft and does vary in various bodies, and therefore the point or degree at 

 which it reaches itt maximum muft vary alfo ; with refpedt to air, I have reafon 

 to think it does not exceed 335 degrees below the freezing point. With ref- 

 peft to other bodies, 72° beneath the freezing point may to moft praftical purpofes 

 be aflumed as the maximum of cold, being the degree at %vhich mercury freezes. 



