Dr. Davy on the Geology and Mineralogy of Ceylon. 323 
exist in the island. I have found all its sub-species, viz. adularia 
including glassy felspar, Labradore felspar, common felspar, and 
compact felspar. All these sub-species are common in gneiss, with 
the exception of Labradore stone, which is very rare ; I have only 
met with it at Trincomalie, in graphite granite. 
7. Of the hornblende family I am only acquainted with two 
species that occur here, common hornblende and glassy tremolite. 
The former is pretty abundant, entering, as it has been already ob- 
served, into the composition of rock ; the latter is rare : I have 
found it only at Trincomalie, in a narrow vein in gneiss. 
8. Pitch stone is the only mineral of the family of this name 
that I have yet seen in Ceylon : near Trincomalie I discovered it in 
a small vein in granite, and I have observed it no where else. 
9. Mica, as an ingredient of gneiss, is of course abundant ; be- 
sides, it often occurs in large plates imbedded in this rock. Common 
chlorite is to be met with occasionally : at Trincomalie I have 
found it disseminated through quartz. 
10. Talc is rare ; the only place where I have yet observed it 
is in the Nitre cave at Doomberawa. 
11. Calc-spar and anhydrite are the only calcareous minerals 
that I have hitherto discovered in gneiss, with the exception of 
dolomite. I met with both the preceding minerals finely crystal- 
lized, in the Nitre cave before alluded to. 
12. Belonging to the inflammable class of minerals, I have 
found only one, viz. graphite, which is pretty commonly dissemi- 
nated in minute scales through gneiss. It occasionally occurs im- 
bedded in this rock in small masses. It is worthy of remark that 
graphite is generally found in company with gems. I have had so 
often occasion to make the observation, that now I never see the 
former without suspecting the presence of the latter. 
It has been asserted that sulphur is found in Ceylon ; but from all 
