376 Royal Society. 



of the mineral by Dr. Thomson, and is said to have been pre- 

 sented by him. I find these crystals to be carbonate of baryta 

 nearly pure, dissolving readily in muriatic acid and leaving 

 an insoluble residue of 0*3 per cent. 



The other specimen is in broad flat pyramids, composed 

 also of a congeries of minute crystals; is grayish, has a pearly 

 lustre, and rests on right rhombic baryto-calcite. These cry- 

 stals were obtained from a mineral-dealer, and are also car- 

 bonate of baryta with a little lime. Lime indeed in this di- 

 strict seems to be very generally associated with the barytic 

 minerals. Carbonate of baryta is exceedingly abundant at 

 Faliowfield lead-mine, is generally of a pure white, and was, 

 till lately, collected and exported in considerable quantity to 

 the potteries in Staffordshire. The trade, however, has de- 

 clined from its being found to contain too much lime. 



It would appear therefore that the name bicalcareo-carbo- 

 nate of baryta must at present be laid aside, being imposed 

 by Dr. Thomson under a misapprehension in regard to the 

 true constitution of the mineral ; and that the sulphato-carbo- 

 nate, if it exists is a much rarer mineral than is generally 

 supposed, and so much resembles the large* crystals of com- 

 mon carbonate of baryta as to deceive the discoverer him- 

 self. 



Durham, April 14, 1837. 



LXXVII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 222.] 



February 2,_" /RESERVATIONS on the Electro-chemical In- 



1837. ^^ fluence of long-continued Electric Currents of 



Low Tension." By Golding Bird, Esq., F.L.S., F.G.S., Lecturer 

 on Experimental Philosophy at Guy's Hospital. Communicated by 

 Thomas Bell, Esq., F.R.S. 



The author, after observing that the brilliant discoveries in electro- 

 chemistry obtained by Sir Humphry Davy were effected by the employ- 

 ment of voltaic currents of high intensity,'elicited by means of large bat- 

 teries, adverts to the labours of M.Becquerel, to whom we are indebted 

 for the knowledge of the chemical agency of feeble currents in re- 

 ducing several refractory oxides to the metallic statef : and also to 

 those of Dr. E. Davy, Bucholz, and Professor Faraday in effecting 

 decompositions of oilier substances by similar means. In prosecuting 

 this branch of inquiry, the author employed an apparatus analogous 

 to that of Professor Daniell, for obtaining an equal and continuous 



• Carbonate of baryta is sometimes met with at Faliowfield in large 

 translucent crystals three or four inches long and two or three in diameter. 



t Details of M. BecquereFs researches will be found in Scientific 

 Memoirs, No. III.— Edit. 



