$68 Mr. Wiseman’s Account of the Effect of 
Of inflammable matter, including the small quantity 
of water contained in the substance 
Of mild calcareous earth - 
Of iron - 
Of earth, tliat appears to be silex - - 
100 
On the Effect of the Mere of Diss, upon 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 leav- 
ing a yellowish powder, which, washed and filtered, was found 
to be sulphur. Vegetable fixed alkali precipitated from the ni- 
trous acid a ferruginous coloured powder, which was iron. 
With a view to determine what length of time was neces- 
sary for the formation of this metallic stain upon flint stones, 
or other substances, I inclosed in a brass wire net the follow- 
ing articles : flint stones, calcareous spar, common writing 
slate, a piece of common white stone ware, and likewise a 
piece of black Wedgwood-pottery. After remaining in the 
water from the summer of 1792 to August, 1795, the flints and 
Wedgwood- ware had acquired the metallic stain in a slight de- 
gree, and the slate had assumed a rust colour ; the other sub- 
stances appeared not to be at all altered. I was greatly surprised 
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, inter- 
grains, 
20.0 
2.0 
36.7 
