368. Proceedings of the Royal Society. 
These augitic traps exist both in the form of narrow dykes, and in 
that of great masses constituting hills. Of the former, the Cum- 
ledge trap-dyke is a good example. _ It is seen in the bed of Oxen- 
dean Burn at Cumledge House, and there forms an amygdaloidal 
greenstone, abounding in veins of zeolite, steatite, and other mine- 
rals. The width of the dyke at this place is about ten yards, The 
average direction of the dyke is NNW. and SSE. It has had the 
effect, as usual, of hardening the strata on each side of it. This dyke 
- has been traced by the author for a considerable distance, running 
through both the old red sandstone and coal formations. It ap- 
pears also to reach into the granite of the Staneshiel and Cockburn- 
Law, 
An amygdaloidal trap is to be seen on the left bank of the Whit- 
adder, below Cockburn Mill, forming a bed of about four feet thick, 
and lying above the old red sandstone strata. There are large ac- 
cumulations of greenstone at Borthwick and Castle Mains. Dunse- 
law is also composed of basalt. 
In the second part of his paper, the author shewed that the granite 
and other felspathic rocks were formed before the deposition of the 
old red sandstones, and the trap-rocks after the deposition of the 
coal-measures, 
Mr Stevenson’s paper was illustrated by a geognostical map, as 
well as by numerous sections. 
3. Notice regarding the Indian Grass Oil, or Oil of Andropo- 
gon Calamus-aromaticus. By Thomas G. Tilley, Phil. D, 
Communicated by Dr Christison. 
Monday, 2d December 1844. 
Sir T. M. BRISBANE, Bart., President, in the Chair. 
The following Communications were read :— 
1. Account of the late Earthquake at Demerara. By W. H. 
Campbell, Esq. Communicated by M. Ponton, Esq. 
2. On the Existence of an Electrical Apparatus in the Flapper 
Skate and other Rays. By James Stark, M.D., Fellow 
of the Royal College of Physicians, Edinburgh. 
3. Observations on the Comet, visible now or lately in the 
Constellation of the Whale. By C. Rumker, Esq. Com- 
municated by Sir T. M. Brisbane, Bart. 
Monday, 16th December 1844. 
Sir GEO. MACKENZIE, Bart., in the Chair, 
The following Communications were read :— 
