TRANSACTIONS OF THE SECTIONS. 65 
range on the south side of the valley, are composed of various trap- 
rocks, among which amygdaloid is pretty common. The cavities of this 
rock are filled up by crystallized minerals, most of them zeolites ; 
these are— 
1. Stellite, first analysed by Dr. T. Thomson and Dr. R. D. Thomson. 
2. Thomsonite, named by Mr. Brooke after Dr. T. Thomson. 3. Natrolite. 
4. Mesolite. 5. Scolezite. 6. Laumonite. 7. Chabazite. 8. Analcime. 
9. Cluthalite, first analysed by Dr. T. Thomson and Dr. R. D. Thomson. 
10. Stilbite. 11. Heulandite. 12. Harmotome or Cross stone. 13. Carbo- 
nate of magnesia, at Bishoptown. 14. Dihydrous peroxide of iron, at Gou- 
rock. 15. Sulphate of barytes. 16. Calcareous spar. 17. Fibrous sulphate 
of lime. 18. Arragonite. 19. Wollastonite, first analysed by Dr. T. Thom- 
son and Dr. R. D. Thomson. 20. Prasolite, named by Dr. T. Thomson. 
21. Fluor spar. 22. Prehnite. 23. Augite. 24. Amphibole. 25. Felspar. 
26. Labradorite, one of the constituents of a variety of greenstone at Campsie 
glen, and at Gleniffer. 27, Mica. 28. Epidote. 29. Steatite. 30. Iron pyrites. 
31. Carbonate of iron. 32. Gray ore of manganese. 33. Kilpatrick quartz, 
first analysed by Dr. T. and Dr. R. D. Thomson. 34. Sulphuret of cadmium, 
rare, and lately discovered, occurring along with prehnite at Bishoptown. Single 
crystals are now selling at 10/. each. It has been analysed by Dr. T. Thom- 
son and Mr. Connel. 
On the Relation of Form to Chemical Composition. 
By Dr. ScHAFHAEUTL. 
The author stated, that he had, in a former communication, given a 
new method of procuring graphite, in which it was also shown that all 
graphites owed their origin to the operation of the same causes ; namely, 
the contact of bitumen (or any similar substance) with a silicate, under 
a certain limited degree of heat; it was further maintained, that the 
compound nature of graphite might be satisfactorily demonstrated, by 
subjecting it to the action of hydrofluoric acid, which, combining with 
the silicon, liberated the carbon of the graphite as a hydruret, which 
was then consumed in the flame of alamp. The object of the present 
paper was to explain the circumstances under which certain modifica- 
tions of form take place in this peculiar substance (as also in others 
generally considered to be elementary), and to prove their connexion 
with changes of an entirely chemical nature. 
A beautiful specimen of a formation of graphite was exhibited to the 
Section, obtained from the Neath Abbey Ironworks, in South Wales ; 
it appeared to be composed of an infinite number of foliated scales 
overlapping each other, after the manner of the slates of a roof, each 
scale being so thin, as to be agitated by the slightest breath of air; a 
second specimen was exhibited of a graphite leaf, where it appeared as 
a globule of much greater size, the laminated structure still, however, 
existing in beautiful development. In a third stage, the scaly structure 
disappeared ; the globule having assumed a more porous and coke-like 
form. Dr. S. having premised an objection to any explanation of these 
curious changes of form, founded merely upon molecular alterations, 
proceeded to detail certain experiments, from which he deduced con- 
clusions of an interesting and important nature. 
1840. F 
