ROTTEX-bTONE. 
53 
fracture slaty, passing into the imperfectly conchoidal* ; hard- 
ness from six to seven (Kirwan. p. 38) : emits a fetid or rather 
nrinuns smell when scraped, nut in a much less degree than the 
following varieties: contains, according to the specimen 
examined, about 18 per ct. of alumine, with small proporlionsf 
of silex, iron, and inflammable matter. 
The next variety of limestone it will be proper to notice, is Other varie- 
one rejected by the workmen at Ashford, as being less fit for 
their purpose than that I have just described. — It appears to be 
too soft to receive a lasting polish, and its colour, though black, 
is much less deep than in the foregoing variety, frequently 
verging on brownish black : texture earthy : fracture slaty ; 
hardness (5 : gives out a very fetid smell on being scraped. One 
specimen of this stone contained, according to the experiments 
made on it, 6 (j carbonate of lime ; 24 alumine j 12 oxide of 
iron; 1 "5 silex ; and 7 inflammable matter. Another speci- 
men of this stone, however, yhom the same led, yielded only I 9 
alumine. 
A third strongly marked variety of limestone, found with the 
foregoing, has tlie following characters : colour black, or 
brownish-black: texture splintery, with disseminated, shining, 
spar-like particles ; these frequently exhibit the minute parts of 
organic remains ; fiacture slaty : hardness 7 : emits a very fetid 
odour, when scraped or rubbed. The specimen analysed gave 
8 per ct. alumine, and 4 silex, with 7 inflammable matter, 
but litile or no trace of iron. 
It must now be observed, that along with these three descri- 
* Hy fracture is here meant the general appearance, or form, whicb 
tlie Inokcii surface of tlie fossil piesents ; bj texture, tlie grain, or form 
and ctispo'ition of the pai tides, observable througliout Uie surface of 
the fracture. 
t In no instance did *be proportion of silex exceed 4 perct. or that 
of tlie iron l§. As ttie experiments, however, which save tliese results, 
were not lepeated on each variety of stone, we do not give these pro- 
portions as tho«e wliicli analysis hereafter may find to be correct. — 
Tire proportion of alumine, in each instance, wo believe, will be found 
to be near the UuUt. 
bed 
