Environs ofLons le Saunter. 151 



their first inspection might leave doubts on their prolongation 

 beneath the mass of oolitic limestone ; I had long observed 

 them before I could decide this question ; but I at last re- 

 marked in some places, and especially to the E. and S.E. of 

 Conliege, an insensible passage of the marly limestone beds 

 into the oolitic beds ; now, the first are subordinate to the 

 marl beds ; it is then evident that they all belong to the 

 same formation. I had moreover occasion to make exca- 

 vations beneath the ferruginous bed, and I always found the 

 marls, which leaves no doubt of the existence of the marl 

 beds beneath the solid beds of oolitic limestone. 



The perfect identity of the beds on each side the valley 

 proves that they have been united, and that they originally 

 formed but one mass. 



The nature and respective dispositions of these mineral 

 masses being well understood, the manner in which the 

 valleys have been formed may be concluded, without having 

 recourse to any hypothesis. 



In fact these mineral masses have been deposited by the 

 waters of the sea : this fact is proved by the marine animals 

 found throughout their whole extent. When the waters 

 abandoned them, the marls must have given way under the 

 weight, now become more considerable, of the mass that 

 covered them ; their slight tenacity offering less resistance 

 than that of the upper masses, the waters carried them 

 away and excavated passages in their mass, forming vast 

 galleries.* 



If we represent to ourselves the considerable thickness of 

 the marls, in some places 100 metres [328 feet], the follow- 

 ing picture presents itself to the imagination : 



An immense platform, under which vast subterranean pas- 

 sages exist, which the waters continue to enlarge, sinks as 



* The character of these valleys would appear to be analogous to tlie 

 valleys on the edge of the oolite escarpment near Batli, A c. For an ac- 

 count of the valleys of denudation on the south coast of Devon and 

 Dorset, consult Prof. Buckland's memoir, in the 1st vol. new series, of 

 the Geological Transactions. (Trans.) 



