T 



333 ] 



B4r. Heat. 



Vol. 



The accuracy of this table even in the lower p.Kt of 

 the fcale is fufficiently apparent by the refult of the 

 experiments of SiiuiTure on ebullition on Mount Blanc; 

 for on that enoripous ir.ounlain, the barometer ftanding 

 at i6 French inches or 17,05 EngHfh, he found watcT 

 to boil at the heat of 68^,993 of Reaumur, a degree which 



on Geneva thermometers is equal to i85°,56 Englifn. 



Hence we fee that difiilktion may be more advantageoufly 

 efFeded on mountains than on plains, and at low barome- 

 trical heights than at the greater, yet within certain limits ; 

 for at heights that furpafs 8 or ro thoufand feet, the fuel,' 

 by reafon of the rarity of the air, is more flowly confi-med! 

 Hence alfo from the knowledge of the degree of the heat 

 of ebullition to two or more decimal places, the ftateof the 

 barometer above or below 212^ may infered to one or 

 more decimal places.— The reafon of this rapid dimi- 

 nution of the heat of ebullition below 25 inches is evi- 

 dently the diminution of refiftance, from the diminifhed 

 weight of the atmofphere, which then is very fenfible; but 

 as the cold continually produced by evaporation is 'then 

 alfo very confiderable, the f/me neceffary to procure ebul- 

 lition is longer as Sauffure remarked on Mount Blanc, 

 vol. vii. in 8vo. § 2oir, p. 328. He found the heat of 

 ebullition barometer 16 to be 68^993 degrees, or in En- 

 glifli meafures barometer 17,05. 185^5 of Fahr. (counting 

 one of Reaumur at Geneva = 2,225 of Fahr.) 



V^"- Tt Hence 



