Botryoidal Limestone with a fœtid smell

We have exhibited the present specimen of limestone as a very curious one, one account of its resembling a bunch of grapes. It seems to be formed by water passing through loose marly earth, and consists of smaller or larger globules, according to circumstances; sometimes in bundles resembling Ketton Stone, (see pl. 8, upper figure,) at other times much larger (see the lower figure in this plate). The globules are occasionally a little hollow, and crystallized within; sometimes nearly clear, and white, when they are destitute of smell; but they are more commonly solid and brown within, have a very fœtid^* odour, easily perceived by scraping or pounding. This smell has been ascribed to bitumen, but is a very different nature. Vauquelin considers it as sulphurated hydrogen. The colour is caused by oxide of iron with more or less clay. The odour goes off from the surface if exposed to the atmosphere; which makes it necessary to scrape it: the heat used in burning it to lime dissipates it entirely.

The lower figure is very intersting, as it shows the stratification while crystallizing, the darker parts making it evident. The top of this specimen is crystallized with the acute tends of the inverse rhomb, (see tab. 4. upper figure,) pointing outwards, which is not unusual in this kind of concentric construction of calcareous earths. Lady Wilson first gave me specimens of this stone, from Sunderland in the county of Durham. Mr. Winch, F. L. S. has since favoured me with many varieties of it from the same place. The Rev. John Harriman sent me a specimen from Hartlepool in the same county; and it should seem by his observations that this curious stratum may extend from Hartlepool to Sunderland, all along the coast, and perhaps much further. It is called Building Hill Stone in Sunderland.