O. A. Derby — Monazite as an Element in Boohs. 109 



We thus have 



9096-8X4-26 



•00000043 



= 90-1218 X10 9 centimeters. 



It is quite within safe limits to say therefore that we should 

 have been able to detect a change of deflection due to the mo- 

 tion of the coil, even though the velocity of the current had 

 been considerably in excess of one thousand million meters per 

 second. 



Physical Laboratory of Cornell University, August 1, 1888. 



Art. XII. — On the occurrence of Monazite as an accessory 

 Element in Rocks / by Orville A. Derby. 



Some five or six years ago Mr. John Gordon, an American 

 mining engineer now engaged in commerce in Rio de Janeiro, 

 brought to my attention a peculiar heavy yellow sand which 

 had been sent to him from the province of Bahia under 

 the supposition that it was tin sand. This on examination 

 proved to be monazite with the composition, according to an 

 analysis by Prof. Henri Gorceix of the Ouro Preto Mining 

 School {Comptes jRendus, 1885) : Phosphoric acid 28 -7 per 

 cent, oxide of cerium 31*3 per cent, oxides of clidymium 

 and lanthanum (?) 39 '9 = 99-9. Inquiries instituted by Mr. 

 Gordon and myself in regard to the locality and mode of 

 occurrence of this sand revealed the fact that it occurs in con- 

 siderable patches on the sea beach near the little town of 

 Alcobaca in the southern part of the province of Bahia, where 

 it seems to have- been accumulated by natural concentration 

 through wave action. 



Attention having been thus drawn to this mineral, Prof. 

 Gorceix has since detected yellow grains in the diamond sands 

 of several localities of the provinces of Minas Geraes and 

 Bahia which from giving the didymium lines in the hand 

 spectroscope have been referred to monazite, and I have my- 

 self identified it by the same process in gold sands from sev- 

 eral points in the provinces of Minas, Rio de Janeiro and Sao 

 Paulo. The wide distribution of the mineral in the sea and 

 river-sands of Brazil was thus established, but under circum- 

 stances that gave no clue to its origin. 



Recently Mr. Gordon informed me that in examining with 

 a lens the sands of the beaches about Rio de Janeiro he found 

 always yellow grains similar in appearance to the Bahia mona- 

 zite and that on concentrating the sands in a copper miner's pan, 

 he obtained a small quantity of white and yellow sand that 



