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pear Jike six-sided prisms; but in fact are only four-sided. 
Two sides are generally smooth and flat, showing the la- 
minated texture and internal pearly lustre; and the other 
two are striated, somewhat convex, and rather irregularly 
bevilled, often giving the crystal a six-sided appearance. 
The summits have also the appearance of being truncated, 
and have various parallel bevillings on them, giving them 
a convexity rather more prominent than that on the sides. 
They are somewhat transparent, and very little coloured. 
The Carbonate of Lime and Stilbite meet, as it were, 
back to back, in the midst of the specimen. There is, how- 
ever, a space which perfectly distinguishes them, the 
Stilbite forming irregular spicule meeting those of the 
Carbonate of Lime. 
The lower specimen is yellower than usual, and the 
crystals are very distinct though small. 
TAB. CCEIX. 
Tue prisms in this specimen are four-sided, and the 
two opposite sides that are parallel to the laminz are 
broader than the other two: they are terminated by a 
four-sided pyramid with rhomboidal faces, which in some 
crystals are truncated at the apex. They line an irregular 
cavity in a fragment of a Basaltic column from the Giant’s 
Causeway. I was favoured with it by John Templeton, Esq. 
