222 Proceedings of Philosophical Societies. [Mancn, 
author supposes of the same era with those which occur near 
Malvern, and at Ludlow and Wenlock-edge, and considers as the 
upper members of the graywacke series, and a link between the 
transition slate-rocks and succeeding formations. 
2. Old red sandstone. 
3. Mountain limestone. . 
4, Coal measures. : 
All the beds of this series are highly inclined, and thrown by 
their undulations into various basins, each of which contains a 
succession of coal-measures surrounded by bands, formed by the 
outcrop of the subjacent beds of mountain limestone and old red 
sandstone. 
The principal of these basins are; 1. That of Somerset and 
South Gloucester, including the collieries of Mendip, Kingswood, 
and Sodbury. 
2. That of the forest of Dean. 
3. That of South Wales. 
The second formation, beginning with the lowest beds, con- 
sists of 
1. Calcario-magnesian conglomerate, and magnesian limestone. 
2. Newer red sandstone and red marl. 
3. Lias. 
4. Oolite, which rises to a greater elevation than the three 
preceding beds, and skirts the eastern border of the district 
under consideration. 
Besides these regular formations, two whin-dykes traverse the 
north border of the Somerset and Gloucester basin, neat Berke- 
ley, extending north and south nearly parallel to each other for 
about two miles, and cutting the transition limestone and old red 
sandstone. At one point, called Woodford, one of these dykes 
has been said to contain organic remains ; but these have been 
found ouly in portions of the limestone, entangled, and partially 
enveloped by the sides of the dyke. This trap contains agates, 
prehnite, sulphate of strontian, carbonate of lime, green earth, 
and ferriferous magnesian carbonate of lime: the two latter 
abound in the amygdaloidal varieties at Woodford. In one 
spot near its south extremity, the dyke becomes columnar. 
This paper contains some precise observations of the angles of 
inclination and direction of the different strata, which, though of 
little importance when taken singly, possess considerable value 
in reference to the structure of an extensive district. 
A note points out the recurrence of magnesian limestone in all 
the formations from primitive dolomite upwards through transi- 
tion limestone, oolite, and chalk, and also that it exists in the 
London clay. An appendix. contains a list of previous works in 
which accounts of the district under examination may be found, 
and the authors have given a very brief but useful abstract of 
these contents. ; 
A paper was read, on the rock of Gibraltar, by Thomas Kent, 
