Addiiio:ial Notes. 5,21) 



Silver Mine in the State of Ncxc-York. \\ 1^^. 



The most consiJerablc mine of either of the j)rcclous me- 

 tals of which the author has heaid in the United States, is 

 the silver mine in the town of Mount-Pleasant, Westchester 

 County, State of New-York. This mine is near the margin 

 of the Hudson, thirty-six miles above the city of New-York, 

 and on land heloging to William Strelt, Esq. It was 

 discovered about tony years ago; and, for some years before 

 the revolutionary war, was wrought to toleiable advantage. 

 The convulsions and derangements attending that struggle 

 suspended the operations of the company engaged in the bu- 

 siness, and they have not since been resumed. 



Geology. 



That the inequality of deelivity cxldbited by the sides or 

 flanks of mountains, in every part of the globe, had any re- 

 gard to the points of the compass, seems to have been first 

 remarked by the celebrated Swedish geologist, Tilas. (See 

 Memoirs of Stockholm for 1760.J But he seems rather to 

 have directed his views to the elevation or depression of the 

 surface of Sweden, than to the bearings of the declivities of 

 mountains in general. Bergman first discovered that the 

 declivities of the flanks of mountains bear an invariable re- 

 lation to their diifercnt aspects. He found that, in mountains 

 extending from nordi to soudi, the western flank is the 

 steepest, and the eastern the gentlest; and that in mountains 

 whicli run east and west, tlie southern declivity is the steepest, 

 and the northern the gentlest. After Bergman, Euffon 

 took notice of the generality of this phenomenon; but his 

 remark was confined to die eastern and western sides of 

 mountains extending from north to south, having no reference 

 to the north and south sides of those which run cast and 

 west. The same fact was afterwards observed, in a general 

 or more partial manner, by Herman, La Metherie, 

 FoRSTER, Pallas, and several others. 



I'owards die close of the eighteenth century, Mr. Kirwan 

 directed his attention to tliis subject, and endeavoured to as- 

 sign the cause of this almost univeisal allotment of unequal 

 declivities to opposite points, and why the greatest arc di- 

 rected to the west and south, and the gentlest to the east and 

 north. He supposes that this fact is connected with the ori- 



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