322 Cursory Remarks on 
texture. close, fine-earthy : fracture slaty, 
passing into the imperfectly conchoidal * : 
hardness from 6 to 7 (Kirwan. p. 38.) : emits 
a fetid or rather urinous smell when scraped, 
but ina much less degree than the following 
varieties ; contains, according to the specimen 
examined, about 18 per ct. of alumine, with 
small proportions + of silex, iron, and inflam- 
mable matter. 
The next variety of limestone, it will be 
proper to notice, is one rejected by the work- 
which are sometimes built of black marble, and in other 
exposed situations, this would frequently be the case, if a 
further decay of the stones were not prevented by a timely 
and friendly covering of lichens aud mosses. I have ob- 
served, however, that pieces of polished marble, though 
equally exposed with those in the unpolished state, do not 
so soon acquire a white crust—Polishing, by filling up the 
minute interstices, induces a greater degree of external 
hardness of the stone and prevents for a longer time the 
decomposition of the surface. 
* By fracture, is here meant the general presto cop or 
form, which the broken surface of the fossil presents : by 
texture, the grain, or form and disposition of the particles, 
observable throughout the surface of the fracture. 
+ In no instance did the proportion of silex exceed 
4 per ct. or that of the iron 14. As the experiments, 
however, which gave these results, were not repeated on 
each variety of stone, we do not give these proportions as 
those, which analysis hereafter may find to be correct.— 
The pruportion of alumine, in each instance, we believe, 
will be found to be near the truth. 
