CASTLK HILL. 
.'57 
had been brought from Newliaven, and was lying 
ill a wliarf near Lewes.* * * § A few months afterwards, 
Mr. A\"ebster, in a geological excursion along the 
Sussex coast, collected a specimen at Newliaven. 
This was analyzed by Dr. Wollaston, and found to 
consist of alumine, in combination with sulphuric 
acid, and a small proportion of silex, lime, and 
oxide of iron. 
This mineral occurs massive, in veins, and in 
tabular and tuberose masses ; the former frequently 
attaining several feet in length, and the latter ex- 
ceeding three or four jiounds in weight. It ap- 
pears to have been of stalactitical origin, and is 
supposed to result from the decomjiosition of iron 
pyrites, and the reaction of other substances. As 
the su])erincunibent strata contain all the elements 
necessary for its production, it probably has been 
introduced into its present situation by intiltration.f 
When pure, it is perfectly white, but is generally 
more or less discoloured by an intermixture of yellow 
clay. It is dull and opaque, with an earthy frac- 
ture, and yields to the knife. It is infusible at 
166° of Wedgwood t, but fuses rapidly when ex- 
posed to the stream of the hydro-oxygen blow- 
pipe : the result is a pearl white translucent ena- 
mel, a partial combustion taking place during its 
fusion. § According to Stromeyer it consists of — 
* Vide Mr. Sowerby’s description of this substance in British 
Mineralogy. 
f Professor Biickland on the Plastic Clay. Geological Transactions 
vol. iv. p. 294. 
t Kirwan. 
§ History of the Gas Blow-pipe, by E. D. Clarke, LL.D. 8vo. 1819, 
p. .56. The experiments of mv brother gave similar results. 
