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acquainted, occupying many distinct stages, have lived in the sea, 

 whilst the plants, so far as I have been able to observe them (broken 

 into fragments), consist of many species irregularly heaped together, 

 the whole, together with the sands, grits, pebbles and shale, offering 

 the clearest signs of the drifting action of water. 



On the subject, then, of the origin of coal, it would appear, that 

 as our inductions can never be sound, if they repose upon one class 

 of phtenomena only, so do some coal strata offer indications of the 

 truth of the hypothesis, that in large tracts of the world, the mineral 

 was formed from vegetables which were washed into bays and es- 

 tuaries, and often carried far into the then existing seas. In other 

 instances, flat and marshy tracts rich in tropical vegetation, being 

 subjected to gradual depressions, may have been converted into 

 lagoons and swamps without any direct encroachment of the sea; 

 and in this peculiar condition (subjected, however, in all cases, 

 to entombment beneath those waters in which the overlying sand- 

 stone and shales were accumulated), oscillations of the land may 

 have raised the beds at intervals, again to be fitted for the growth 

 of marshy vegetables. 



In geology more than any other science, it must be our constant 

 endeavour to unravel phsenomena which at one time seemed inexpli- 

 cable, and often opposed to each other ; but with new discoveries 

 the difficulties vanish, and the apparently conflicting testimonies are 

 found to be in perfect harmony with the order of changes, which 

 the surface of the globe has undergone. I repeat, therefore, my 

 belief, that, whilst coal may have been formed in many localities 

 by subsidence of vegetables on the spot on which they grew, as first 

 suggested by Bi'ongniart, MacCulloch and others, its origin unques- 

 tionably is also due, and over very large territories, to plants having 

 been washed into estuaries and seas, and there equally spread out in 

 successive layers with sand and mud. 



Gypsiferous Rocks in North America, — Having now disposed 

 of all the subjects relating to the known deposits of decided Palse- 

 ozoic age in North America, I will endeavour to show how the ex- 

 amination of one continent throws light upon the structure «of an- 

 other, by inviting your attention to the great Gypsiferous deposits 

 of North America, to which, in treating of Russia, I have already 

 alluded. 



The gypsiferous strata of Nova Scotia, with their associated sand- 

 stone, shale, and fossiliferous limestones, were at first referred by Mr. 

 Logan to the triassic period ; an inference which he drew from the 

 general character of the fossils, and their dissimilarity, as a whole, 

 to those of the Carboniferous rocks of that country. This opinion, 

 however, is one from which I know this author receded, upon finding 

 that some of the shells which he had brought home were recognised 

 by M. de Verneuil and Count Keyserling, to be identical with species 

 from the Permian deposits of Russia. 



This comparison with the Russian strata has, indeed, received so 

 much illustration by the arrival of a large assemblage of fossils 

 brought from numerous localities in Nova Scotia by Mr. Lyell, 



