VOL. LXXXVIII.] PHILOSOPHICAL TRANSACTIONS. 421 



XXIII. Of a Substance found in a Clay-pit; and of the Effect of the Mere of 

 Diss, on various Substances immersed in it. By Mr. Benj. Wiseman, of Diss, 

 Norfolk. Communicated by John Frere, Esq., F. R. S. With an Analysis of 

 the Water of the said Mere. By Charles Hatchett, Esq., F. R. S. p. 567. 



This substance was found near Diss, in a body of clay, from 5 to 8 feet below 

 the surface of the soil. All the pieces lay nearly in an horizontal direction; and 

 varied in size, from 2 or 3 oz., to as many lb. The colour of the substance, 

 when taken fresh from the clay- pit, was like that of chocolate; it cuts easily, and 

 has the striated appearance of rotten wood. The pieces were of no particular 

 form ; in general, they were broad and flat, but I do not recollect to have met 

 with a piece that was more than 2 inches in thickness: it breaks into laminae, be- 

 tween which are the remains of various kinds of shells. The specific gravity of 

 this substance, dried in the shade, is 1.588; it burns freely, giving out a great 

 quantity of smoke, with a strong sulphureous smell. By a chemical analysis, 

 which I cannot consider as very accurate, 100 gr. appear to contain, 



Of inflammable matter, including the small quantity of water contained in the 



substance 41.3 grs. 



Of mild calcareous earth 20.0 



Of iron 2.0 



Of earth, that appears to be silex 36.7 



100 

 On the effect of the Mere of Diss, on various substances. 



Observing several years ago, that flint stones taken out of the Mere of Diss 

 were incrusted with a metallic stain, I was induced to make some experiments, in 

 order to discover the nature or composition of this metallic substance. Nitrous 

 acid readily removes it, dissolving a part, and leaving a yellowish powder, which, 

 washed and filtered, was found to be sulphur. Vegetable fixed alkali precipitated 

 from the nitrous acid a ferruginous coloured powder, which was iron. 



With a view to determine what length of time was necessary for the formation 

 of this metallic stain on flint stones, or other substances, I inclosed in a brass 

 wire net the following articles: flint stones, calcareous spar, common writing 

 slate, a piece of common white stone ware, and a piece of black Wedgwood-pot- 

 tery. After remaining in the water from the summer of 17 92 to August, 1795, 

 the flints and Wedgwood-ware had acquired the metallic stain in a slight degree, 

 and the slate had assumed a rust colour; the other substances appeared not to be 

 at all altered. I was greatly surprized to find the copper wire that held the net, 

 surrounded with a metallic coating of a considerable thickness; it was of a deep 

 lead colour, and of a granulated texture. When taken from the wire, and ground 

 in a mortar, it had a black appearance, interspersed with very hard shining parti- 

 cles. The wire was evidently eroded, and this substance deposited in the place 

 of the copper that was decomposed, somewhat similar to the decomposition of 

 iron in cupreous waters. By repeated chemical analysis of this substance, 100 

 gr. contain, of copper, 70; of sulphur, 16.6; of iron, 13.3 gr, 



