CXXU PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



oue country not for the repetition of the strata, bed by bed, of another, 

 but simply for the representative strata deposited simultaneously with 

 them ; nor is this all, as they are also fully aware that the alteration 

 of the mineral and physical conditions of the strata must have been 

 attended with a similar variation in the groups of organic beings, or 

 in the relics which they have left of their existence. To determine 

 the age of a drift-deposit must always require peculiar caution, as the 

 organic remains of a previous deposit may so readily have been washed 

 into it ; whilst, at the same time, conform ability of stratification can 

 in such cases form no sufficient evidence for uniting the upper to the 

 lower, as experience shows us that the drift-deposits of our own 

 coasts would assume a parallelism of position were they thrown up 

 against a sloping bank or bed. It is necessary, therefore, to pass be- 

 yond the limits of the drift-deposits, and to make the inquiry in these 

 localities where other deposits indicating a state of tranquillity may 

 from their position be fairly considered as coincident in time with the 

 drift. This is the course pursued by our most able geologists, in- 

 cluding Sir Charles Lyell, although Mr. Kelly objects to this modus 

 operandiy observing, ^' This is my view of the Devonian system: had it 

 been composed of a regular succession of rocks, lying together like 

 the Silurian system, or like the Carboniferous formation, there would 

 be no doubt about it ; but to make it good, instead of working it out 

 in Devon, its own country, one of the most profound geologists found 

 it necessary to ransack Europe, to get suitable parts to make it up ; 

 and it appears to me that Sir Charles Lyell undertook no easy task, 

 when he took a limb from Dura Denn, a joint from the cornstoiies 

 of Herefordshire, an arm from the green chloritic slates of Cornwall, 

 a leg from the grey sandstones of Cromarty, and a part from the 

 Eifel limestone, and endeavoured to join these distant fragments 

 together and make out of them a consistent whole." Without doubt 

 the task was and is difficult, as that of the correlation of the strata 

 of any epoch in distant countries must necessarily be ; but, though 

 difficult, it is the reasonable and proper task of the modern geologist. 

 The yellow sandstone of Dura Denn, Fife, is classed by Sir C. Lyell 

 as the upper member of the Upper Devonian, and is considered also 

 by Mr. Kelly as the equivalent of the upper part of the so-called 

 Irish Old Red ; but, as by him this yellow sandstone ought not in 

 Ireland to be separated from the Carboniferous, he concludes that the 

 other subdivisions enumerated by him in the Irish Old Red should 

 also be classed with the Carboniferous formation. To establish a 

 community of fossils, Mr. Kelly quotes a peculiar red sandstone 

 in the Kildress River, county of Tyrone, as yielding many common 

 Mountain-limestone fossils, this sandstone being, in his opinion, near 

 the base of the Old Red in that locality ; but it appears to me that 

 this sandstone requires further examination before it can be ad- 

 mitted as a sufficient proof. The brown-stone conglomerate, usually 

 classed with the Old Red, and differing from it in nothing but a more 

 rusty-brown colour, lies indeed conformably on the Tyrone schists 

 with Graptolites, but has hitherto in that locality yielded no fossils of 

 any description : Mr. Kelly, however, considers it identical with other 



