O'Eeilly — On the Comtitution of C alp Shale. 565 



part of the Carboniferons limestone in Ireland. It is not, however, 

 clearly explained in what particular locality or province the term 

 " Calp " originated, or was applied, to these particular rocks; nor can 

 it at present be stated to what language the word properly belongs, 

 and what is its true and proper signification. 



It is remarkable that Kirwan should have taken into consideration 

 the coloiu' of the shale as it usually presents itself eitlier in the quarry 

 or in buildings as a stone. This character struck me, since having 

 observed that there is nearly always present iron pyrites in minute 

 crystals, I remarked the continuous decay and exfoliation of the 

 stones where exposed to the atmosphere, though without any appear- 

 ance of oxydation so far as the iron is concerned. I was consequently 

 led to examine more attentively the constitution of the shale, and 

 taking at haphazard the first specimen that came to my hand, I treated 

 it with HCl with a view to determining the nature of the insoluble 

 residue. This I found to be abundant, flocculent, and of a dark brownish 

 colour. The density of this part was low and not immediately ex- 

 plainable as characterising a purely sedimentary rock. Having con- 

 tinued to separate this insoluble portion of the shale, I had enough to 

 enable me to have a complete analysis made of it by Mr. Wm. L. 

 Warren, f.c.s., and obtained from him the following as his ileport 













Percentage 



SiOj, 62-01 



Feo^Oa, . 











4-87 



FeO, . 











0-06 



Al.Os, . 











15-05 



CaO, . 











9-95 



MgO, . 

 MnO, . 











3-25 

 0-12 



CuO, . 











trace 



Na^O, . 











3-01 



K,0, . 











0-40 



S, _ . 



, 







1-06 



Chemically c 



Dmbin 



ed mc 



nsture, 





0-36 



100-14 



It is evident that in this analysis the sulphur is to be counted as 

 iron pyrites, while some of the lime may be accountedfor by the incom- 

 plete removal of that constituent of the rock by the action of the HCl. 



2 E 2 



