GEOLOGY. 255 



which is a mark of the Myadae, or such burrowing bivalve shells, and 

 not of the true Unionidse ; they also differ in the interior. Seeing 

 that in these cases quietly deposited limestones with marine shells 

 (some of them indeed of estuary character) rest upon beds of coal, 

 and that in many other cases purely marine limestones alternate fre- 

 quently with layers of vegetable matter and coal, may we not be led 

 to modify the theory, founded on the sound observation of Sir TV". E. 

 Logan, by which the formation of coal has been rather too exclu- 

 sively referred to terrestrial and fresh-water conditions ? May we 

 not rather revert to that more expansive doctrine, which I have long 

 supported, that different operations of nature have brought about the 

 consolidation and alteration of vegetable matter into coal ? In other 

 words, that in one tract the coal has been formed by the subsidence 

 in situ of vast breadths of former jungles and forests ; in another, by 

 the transport of vegetable materials into marine estuaries; in a third 

 case, as in Russia and Scotland, where purely marine limestones al- 

 ternate with coal, by a succession of oscillations between jungles and 

 the sea ; and, lastly, by the extensive growth of large plants in shallow 

 seas. 



The geological map of Edinburghshire, prepared by Messrs. Howel 

 and Geikie, and recently published, affords indeed the clearest proofs 

 of the frequent alternations of beds of purely marine limestone charged 

 with Producti and bands of coal, and is in direct analogy with the 

 coal-fields of the Donetz, in Southern Russia. 



Concerning the Permian Rocks which were formed towards the 

 close of the long palasozoic era, and constitute a natural series of the 

 old Carboniferous deposits, it has recently been shown that they pre- 

 sent in little England nearly as great diversities of lithological struc- 

 ture as those which distinguish the strata of the same age in Eastern 

 Russia in Europe from the original types of the group in Saxony and 

 other parts of G erinany. 



Sir R. I. Murchison further stated that, from recent geological re- 

 searches, it would appear that in the southern hemisphere there is 

 not merely a close analogy between the rocks of the Palaeozoic age 

 and our own, but, further, as far as the Mesozoic formations have 

 been developed, they also seem to be equivalents of English typical 

 Secondary deposits. 



This existence of groups of animals during the Silurian, Devonian, 

 Carboniferous, and even in Mesozoic periods, in Australia and New 

 Zealand, similar to those which characterize these formations in Eu- 

 rope, is strongly in contrast with the state of nature which began to 

 prevail in the younger Tertiary period. We know, from the writings 

 of Owen, that at that time the great continent at our antipodes was 

 already characterized by the presence of those marsupial forms which 

 still distinguish its fauna from that of any other part of the world. 



GEOLOGY OP THE COUNTRY BETWEEN LAKE SUPERIOR AND 



THE PACIFIC. 



At a recent meeting of the London Geological Society, Mr. James 

 Hector communicated a paper giving the geological results of three 

 years' explorations of the British territories in North America along 



