Prof. Olnibted on the Gold Mines of North Carolina. 375 



which would be counteracted by 16'35 inches of zinc. But as 

 this cannot be apphed without adding more iron, the zinc 

 must be increased by so much as will also counteract that ad- 

 dition ; and yet the zinc must not be greater or less in length 

 than the iron added. The exact cjuantity I make to be 27*92 

 inches. 



The expansion of pendulum rod will then be for 1° Fahr. 

 3 in. steel -000022830 

 36-139290 iron -000250600 

 27-92 iron •00019354 -2 



67-059290 in. -0004.66972 of 27-92 inches zinc will be 



•0004.66822. 



Having determined the length of zinc necessary, I apply it 

 thus : — The pendulum rod is made as usual in common clocks, 

 with three inches of steel spring attached to an iron wire, 

 having a foot firmly fastened to it ; — a tube of zinc 27*92 

 inches long, is slid over this rod and fastened to the foot : an 

 iron tube is now put over this zinc tube, and at the top is fixed 

 by a screw to the top of the zinc; the bottom of the iron tube 

 is connected with the pendulum ball. — The annexed view will 

 convey a better idea of the nature of the instrument than any 

 verbal descrij^tion. 



A is the watch spring. 



B the iron wire. 



C the zinc tube. 



D the external iron tube. 



E E the screw collars for regulating the zinc tube. 



F the screw for shortening the whole rod. 



LX. On the Gold Mines of North Carolina. By Denison 

 Olmsted, Professor of Chemistry and Mineralogy in the 

 University of North Carolina *. 



''pi IE gold mines of North Carolina, which have recently 

 -^ become an object of much inquiry both at home and 

 abroad, are situated between the 35th and 3()th degrees of N. 

 latitude, and between the 80th and 81st degrees of W. longi- 

 tude from London. They are on the southern side of the 

 State, not far from the borders of South Carolina, and some- 

 what westward of the centre. Through the gold country 

 flows the river Petlec, receiving within tlie same district, the 

 IJwharre from the north, and Uocky River from the south, 

 both considerable streams. Above the junclion with the 

 I'wharre, the Pedee bears the name of Yadkin, 



The gold country is spread over a space of not less than 

 • I'Vom the Aiiicriraii Joiinial ol' Science ami Arts : vol. ix. 



1000 



