CXXXV1 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



pressed upon my mind by the great number of local species which 

 that eminent conchologist, Dr. Lea of Philadelphia, has even re- 

 cently established and described. The object of another paper of 

 Professor Phillips was, in a great measure, to bring under the notice 

 of geologists the great difference in mineral aspect, and the only partial 

 agreement in fossils, of the oolitic regions of North Yorkshire and the 

 South of England, and, whilst attempting to settle the real affinities 

 of some of the calcareous beds in the Yorkshire series with some of 

 the well-established members of the Oolitic group of the South of 

 England, to facilitate the determination of the geographical range of 

 the ironstone, coal, and limestone of Yorkshire, and of the physical 

 conditions of the sea or estuary in which they were deposited. 

 "When I observe that, by the close examination of two great general 

 sections, Professor Phillips has proved the existence in the lower 

 oolitic series of five distinct plant-bearing bands of sandstones, of 

 shales which occasionally yield coal arranged in three zones, of four 

 calcareous bands, and of several layers of ironstone, it must be 

 admitted that he has brought before us most remarkable alterna- 

 tions in the physical forces in action at the time ; but he has 

 gone still further, by describing the geographical range or distri- 

 bution of these varied deposits, and tracing out the relation of the 

 lines of deposition, called by him " isochthonal lines," with the 

 general strikes and dips of the strata, or in other words the lines 

 which mark the limits of each varying condition of the deposits, 

 from marine to estuarine. I need not enter further into the details 

 of this paper ; but I may observe that, as Professor Phillips proposes to 

 resume, at a future period, the discussion both of the geographical 

 range of the fossils, and of the physical conditions of the sea-bed 

 already glanced at in this paper, he affords us another proof of the 

 high advance in geological science of the present day. At one time 

 it was supposed that palaeontology had entirely done away with the 

 necessity of studying the mineral characters of deposits ; but now we 

 find that the mineral character is essential for the right understand- 

 ing of the fossils, as indicating the physical conditions under which 

 they have been deposited. 



A portion of the same geological division of strata engaged the 

 attention of Mr. A. Geikie, one of the members of the Geological 

 Survey of Great Britain ; and the results of his investigations are 

 given in a paper on the Geology of Strath, Isle of Skye. The 

 previous writers on this somewhat complicated district are enu- 

 merated, namely, Jamieson, Macculloch, Murchison, and Edward 

 Forbes, — the first of the latter two writers having, however, been 

 principally instrumental in determining the existence and limits of 

 strata belonging to the lias, and the lower and middle oolite, whilst 

 Edward Forbes, in seeking for the equivalents of the English has and 

 oolite, ascertained that the Oxford clay has its equivalent in Skye. 

 The district examined by Mr. Geikie is a narrow belt, from three to 

 six miles in breadth, which extends across the narrowest part of the 

 island from sea to sea, and in area is about thirty square-miles. 

 Including, as it does, the largest development of the lias in Scot- 



