JnalyjisofantmVayielyofLeadOn. 4ig 



at Tcry remote periods, and in very difFerent climates. This difference may be attributed 

 to the nitrous gas, which is ufually made ufe of. It is allowed, that experiments of this 

 kind cannot be compared, if any alteration happens in the water made ufe of; or in the 

 nitrous gas ; or in the dimenfions of the tube j or in the manipulations. Correftions 

 founded on fuppofitions, very far from being juftified by experiment, are very feduloufly 

 applied, and regular methods are rejected, to which no exception has ever been made but 

 what has been overthrown by aftual obfervation. Perhaps they are found too Cmple ia 

 Europe. 



And, indeed, how can it be imagined that the atmofphere, which is continually 

 agitated by motions that fuddenly remove its parts, and which renew and alter its Ctua- 

 tions, can vary confiderably between one village and another. There is, however, an 

 exception to be made for thofe places which are elevated above the level of the fea. The 

 difference of fpccific gravity between oxigen and azote gas, which in the elaftic ftate 

 exert a very vi'eak mutual a£lIon, explain that difference which has been found in their 

 proportions. 



VI. 



Analyjis of a new Variety of Lead Ore. By Richard Chekuvix, Esq. Communicated 



by tlie Author. 



T, 



HE mutual elucidation which kindred fciences receive from each other, muft ever 

 increafe as the means of invefligation become more accurate and extenfive, and in no 

 inftance can this mutual connexion and improvement be more ftrikingly difplayed, than 

 when the influence of newly difcovered fadts extends itfelf through the whole dominion of 

 natural knowledge. 



When Sir Ifaac Newton, by comparing the refrafling power of water with that of other 

 bodies, made the bold inference that it confifted partly of inflammable matter, and that 

 the diamond poffeffmg that power in a ftill higher degree, muft be ranked among com- 

 buflible fubftances, it was little fufpefted that chemiftry would prove this not to be the 

 vague doubt of an imagination niifled by a favourite hypotheGs, but the firm aflertion of 

 genius guided by ftrong analogical convl£tion. The progrefs made fince that period affords 

 numerous examples of fuch happy coincidences ; and it cannot fail to be highly fatisfa£l:ory, 

 when two fciences, tending to the fame point by different means, concur in affording 

 fimilar refults. The Abbe Hauy, on eomparifon of the cryftalline form of the emerald 

 and the berll, after Monf. Vauquelln had juft difcovered his new earth in the latter, did 

 not hefitate to pronounce his ftrong fufpicion of its being a conftitucnt part of both } and 

 analyfis proved the validity of his opinion. I am happy that I have it in my power to 

 furnifli another example of the accuracy of thofs principles, to which he has fo particularly 



F f a d€voted 



