6 M. Beaunier on the 



rior parts, that is to say, the points furthest removed from 

 the surface, are placed precisely under those parts of the 

 coal formation that are at present the highest ; a fact that has 

 been observed in many other countries, but from which the 

 singular and rigorous conclusion has not perhaps been drawn, 

 that the lowest part of the primitive rocks on which the coal 

 formation is deposited, answers precisely to those parts of the 

 latter, which are at present the most elevated ; or reversing 

 the proposition, that the last valleys cut in the coal measures 

 cover ridges of primitive rocks concealed beneath them. 

 This sketch, which is perhaps new, supposes certainly what 

 many geologists are inclined to doubt, namely, that the beds 

 in the coal formation are at present in the same situation as 

 when they were moulded in the primitive rocks.* 



This supposition seems to us supported, with respect to the 

 country in the vicinity of St. Etienne, by so many facts, that 

 we have not been able to refuse it credit — we shall present 

 the following considerations. 



1. When the coal beds, or the beds of the measures, are 

 highly inlined, it generally happens that their thickness in- 

 creases with their depth. An analogous effect would take 

 place with regard to matters deposited on inclined planes. 



2. When the lowest deposits of a secondary country have 

 been formed by large fragments with little or no adhesion, it 

 follows that these matters have rolled into the hollows of the 

 primitive country, so as partly to fill them up, forming a less 

 inclined talus upon which beds of sandstone, schist, and 

 coal have been deposited, which then would naturally be 



* Although it does appear that the irregularities of St. Etienne coal 

 measures may be owing to the uneven surface of the primitive rocks be- 

 neath, yet it is almost needless to remark that faults and many contor- 

 tions must have originated from other causes ; for example, no possible 

 inferior surface on which the coal measures could have been deposited, 

 could at all have formed the twistings and contortions of the coal mea- 

 sures from Broad Haven to Gouldtrop Road, in St. Bride's Bay ; they ap- 

 parently arise from the trap, which rising from beneath the old red sand- 

 stone, overflows the coal measures and squeezes them up against the grey- 

 wacke. I have forwarded sections, &c. of this remarkable coast to the 

 Geological Society in an account latel;' drawn up by Mr. Conybeare and 

 myself on the Geology of Southern Pembrokeshire. (Trans.) 



