180 



explanation, is magnified. This fossil lines the cavities 

 of a sort of Kragg of Kirwan. The same crystals are also 

 found at Salisbury Craig, Edinburgh. The substance is 

 sometimes found amorphous, as at King's Park. 



TAB. CXCIV. 



1 his was sent me by my friend G. Laing, Esq., from 

 Hartfield near Paisley. It is a fine specimen showing 

 the green side of the radii, and the crystals in nearly re- 

 gular four-sided columns, with two opposite truncations at 

 the apex ; these truncations, or secondary faces, are the same 

 as those in the former description, tab. 193, on the upper 

 edges, and ought to be particularly remembered, as they 

 assist in forming a very singular modification, which will 

 be shown in 



TAB. CXCV. 



1 his specimen came from the same place as the last, and 

 leads to a curious modification. The crystals are arranged in 

 double stellated groups, the radii of each extending so as 

 to meet at the edges, like the spokes of two wheels placed 

 against each other, contrary to their position on carriages ; 

 the periphery of the wheels coming together ; the edges form- 

 ing one circular face ; see the left- and right-hand figures . 

 These are grouped among roughish indistinct semi-orbicular 

 masses. The colour is not so attracting as the formation, 

 being dull and brownish. This mineral is formed in the 

 cavities of Kragg rock somewhat approaching Porphyry. 

 The crystals are nearly similar to those of tab. 193, but 

 the secondary faces being larger, the terminal one is lost 

 in an edge. 



