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There is no break between the Upper Silurians and the Lower Silurians ; 

 and none between the Upper Silurians and the old Eed Sandstone ; 

 or between the old Red and the Carboniferous deposits. All these rocks 

 pass conformably, in certain localities, one into another. In the Lower 

 Ludlow rock of the Upper Silurians, however, and two thousand feet 

 below the uppermost beds of the Silurian formation, a fish, the Pteraspis 

 Ludensis, has been detected; while in the uppermost deposits the seed 

 vessels of land plants have been found. The remains of fish and 

 terrestrial plants are abundant in the old Bedrocks; and the Carboniferous 

 strata yield the remains of the most profuse terrestrial vegetation the world 

 ever beheld, the remains of insects and of land shells and reptUes. In 

 the Permian rocks, traces of birds are known by their footprints ; and in 

 strata of the age of the Trias, the base of that great series of secondary 

 deposits which includes the Lias, the Oolite, and Chalk, we find the 

 first discovered relics of a mammal, the Microlestes of Pleininger. The 

 Tertiary formations with their long periods of Eocene, Miocene, and 

 Pliocene, exhibit marvellous and numerous forms of quadrupeds, which 

 have long since passed away. The enormous lapse of ages that must have 

 passed between the close of the Pliocene period, and the recent or present 

 period, may be gathered from the fact that the immensely protracted 

 Glacial period intervened, with all its arctic and subarctic phenomena, and 

 which must have extended over many thousands of years. It is with the 

 maximum development of this epoch that our first drift deposits must be 

 correlated. "We have evidence that during the Pliocene period the warmth 

 of northern latitudes slowly decreased, until during the maximum of the 

 Glacial period the cold became so intense that we must look to Antarctic 

 rather than Arctic phenomena to explain the history presented to the 

 student of Glacial phenomena. It is well to refresh our memories with 

 a perusal of Antarctic voyages ; and to remember the history of the 

 Antarctic regions at the present time, when Ice holds fast, in his geUd 

 grasp, the land of Victoria and Erebus, as in one vast glacier. "We know, 

 from Mr. Dabwik, that immense glaciers are found in the latitude of Paris, 

 and that icebergs, and ice floes, drift with their burdens hundreds of miles 

 further towards the equator, than they do when drifting from the north. 

 Erom all we gather, the history of the Arctic and subarctic latitudes, 

 during the Glacial epoch, was that of the present Antarctic character and 

 influences. The Antarctic regions are chiefly covered by the ocean, and 

 the great waters prevail towards the tropics ; and so, during the Glacial 

 epoch, there was no doubt a far larger area of sea in the north temperate 

 regions by some thousands of square miles than at present; and the 

 sea as far south as Austria in Europe, and Pensylvania in America, must 

 have been traversed by ice floes, packs, and bergs. "I venture to 



