Dr Turner's Chemical Examination of Wad. 21^ 



AiiT. III. — Chemical Examination of Wad. By Edward 

 Turner, M. D., F. R. S. E., Professor of Chemistry in the 

 University of London. * Communicated by the Author. 



As the subject of this notice has never been found crystal- 

 hzed, and, from its aspect, appears to want that definite con- 

 stitution which imparts so much interest to the analysis of 

 most other minerals, it has hitherto been almost entirely ne- 

 glected by chemists. I have myself been induced to examine 

 it solely from its being enumerated among the ores of manga- 

 nese, to which my attention has been much directed within 

 the last two years ; and my apology for introducing it to the 

 notice of the Royal Society, is its connection with the essay 

 on the oxides of manganese, which was honoured with a place 

 in the last volume of their Transactions. 



Under the name of Wad, or Black Wad, are comprehended 

 several minerals, which are distinguished by the following 

 characters : — They are soft, light, and porous, more or less 

 earthy in appearance, of a brown colour, soil by contact, and 

 contain manganese. Though they agree in these general 

 points of resemblance, several of them are distinguishable from 

 each other by physical properties, and differ essentially in che- 

 mical constitution. 



. First species. Wad from Upton Pyne in Devonshire. 



For this Wad I am indebted to the kindness of Mr Konig 

 of the British Museum. It occurs in a curved tabular mass 

 about half an inch thick, and may be easily separated into 

 thinner laminae. It is easily broken, is considerably softer than 

 ; gypsum, and soils when handled. Its colour is brown with a 

 shade of yellow, somewhat like that of bismuth. The lustre of 

 a fresh surface is considerable, and rather metallic. The streak 

 is brown and shining. It consists of small scaly particles, ar- 

 ranged together so as to give to a broken surface a fibrous ap- 

 pearance. It is very porous, and emits numerous air-bells 

 with a hissing noise when put into water. Its specific gravity, 

 after being boiled in water, is 2.314. 



* Read before the Royal Society of Edinburgh, 1st February 1830. 



