146 Prof. A. C. Ramsay on the [Jan. 29, 



The author then alludes to the subject of two papers by himself, given 

 to the Geological Society in 1871, on the Red Rocks of England, in 

 which he attempted to show that the Old Red Sandstone, Permian, and 

 New Red series were all deposited in great inland lakes, fresh or salt ; 

 and this, taken in connexion with the wide-spreading terrestrial cha- 

 racter of much of the Carboniferous series, showed that a great con- 

 tinental age prevailed over much of Europe and in some other regions, 

 from the close of the Silurian epoch to the close of the Trias. He then 

 endeavours to show the value of the time occupied in the deposition of 

 the above-named formations, when compared with the time occupied in 

 the deposition of the Cambrian and Silurian strata, and of the marine 

 and freshwater strata which were deposited between the close of the 

 Triassic epoch and the present day. 



After alluding to the probable mixed estuarine and marine character 

 of the purple and grey Cambrian rocks of St. David's, it is shown that the 

 Cambrian and Silurian series may be massed into three great groups: 

 first, from the bottom of the purple Cambrian rocks to the top of the 

 Tremadoc slates ; these being succeeded unconformably by the second 

 group, the Llandeilo and Bala or Caradoc beds ; on which rest uncon- 

 formably the members of the third series, ranging from the base of the 

 Upper Llandovery to the top of the Upper Ludlow beds, each uncon- 

 formable break in stratigraphical succession being accompanied by a 

 corresponding break in palaeontological succession. 



These three great divisions are next shown to be comparable, in the 

 time occupied for their deposition, to the three divisions of Lower, 

 Middle, and Upper Devonian rocks, which are considered to be the 

 marine representatives of the Old Red Sandstone ; and therefore it 

 follows that the time occupied in the deposition of the latter may have been 

 as long as that taken in the deposition of the Cambrian and Silurian series. 

 This position is strengthened by the great palseontological differences in 

 the fossils of the Upper Ludlow and those of the marine Carboniferous 

 series, which seem to indicate a long lapse of time during which, in 

 Old Red Sandstone areas, no direct sequence of marine deposits took 

 place. 



The next question considered is, what relation in point of time the 

 deposition of the Old Red Sandstone may have taken, when compared 

 with the time occupied in the deposition of certain members of the 

 Mesozoic formations. Through a series of arguments, lithological, 

 Btratigraphical, and palaeontological, the conclusion is arrived at, that the 

 whole of the Liassic and Oolitic series present the various phases of one 

 facies of marine life, and, in this respect, are comparable to the changes in 

 the fossil contents of the various subformations of the Cambrian and 

 Lingula-flag series, of which the Tremadoc Slates form an upper 

 member. In like manner the Lias and Oolites may be compared 

 with the Lower Devonian strata ; and therefore a lower portion of the 



