62 Geological Society. 



he never would have entered, as it were alone and single-handed, 

 on so irksome and laborious an investigation. That the work is in 

 many respects imperfect must be admitted, but considering the ap- 

 parent disproportion of his means to his end, it is surprising that the 

 author should have achieved so much : what he has left incomplete 

 or inaccurate will be readily supplied and corrected by the supple- 

 mental labours of more fortunate observers, when the physical fea- 

 tures of this extensive tract shall have been accurately delineated by 

 the Ordnance Department. 



For a detailed account of the carboniferous tracts in Salop and 

 the adjacent counties we are indebted to Mr. Murchison. The fol- 

 lowing are the conclusions which his paper tends to establish. 



1. In the Shrewsbury coal-field the presence of a younger se- 

 ries of coal-measure than has hitherto been noticed, characterized 

 by the freshwater limestone above alluded to. 



2. The recurrence of these beds at Coalbrook Dale, over an older 

 series of coal-measures which at one spot repose on mountain lime- 

 stone, at other places either on the old red sandstone or on transi- 

 tion rocks. 



3. The absence of these upper beds at the Titterston Clee hills, 

 where the lower beds rest in two places on mountain limestone, but 

 generally on old red sandstone, as they do invariably on the brown 

 Clee hill, in the forest of Wyre and at Newent. 



4. In some of the poor and ill-consolidated coal-beds, particularly 

 in the upper part of the series, the characters of the fossil plants, both 

 generic and specific, can be recognised in the coal itself. 



5. The mountain limestone where it does occur in this part of the 

 country is of inconsiderable thickness, and wedge-shaped, so that it 

 shortly disappears entirely. Its absence, therefore, is not to be im- 

 puted to mighty convulsions, but to partial and scanty deposition in 

 the first instance. 



At Shaftoe, near Wallington, in Northumberland, Mr.Trevelyan* 

 has observed among the constituents of the millstone grit, the low- 

 est bed of the regular coal-measures, transparent fragments of gar- 

 net j they occur there rather abundantly. He has also remarked 

 in other northern coal-fields small portions of hornblende in a simi- 

 lar situation. 



The Rev. Mr. Williamson has directed attention to certain ra- 

 vines in the Mendip hills, and other heights which bound the coal- 

 field of Bristol. These ravines cross the ridges transversely so as 

 to connect the opposite valleys, being occupied in part by horizon- 

 tal beds of dolomitic conglomerate and lias $ he infers that the frac- 

 tures took place before these rocks were deposited, and that the 

 bone-caves were formed at the same period. 



Dr. Lloyd first observed fossil fishes in the old red sandstone. Mr. 

 Murchison finds the observation true over a considerable extent of 

 country -, they belong chiefly to the genus Cephalaspis of Agassiz j 

 they have also been described by Dr. Fleming, as having been met 



• Lond. and Edinb. Phil. Mag. and Journ. of Science, vol. vi. p. 76, (1835.) 



