18 STEATIGRAPHICAL GEOLOGY. 



tremely slow, so slow, that a foot may represent a thousand years, or even more. 

 The shales, clays and marls may have been deposited with greater rapiditj^; but 

 when we consider, that the change from one kind of rock-forming material to an- 

 other indicates a break in the continuity of time, and that great lapse of time was 

 necessar}^ for the growth of the marine and land vegetation, which formed the coal 

 found between beds of clay and shale, we are led to the conclusion, that the time 

 which elapsed between two separate beds of cla}^ and shale, or marl, added to the 

 time necessary for the deposition of their materials, will, on the whole, make their 

 formation as slow as that of the limestones. The sandstones and conglomerates, 

 particularly those of the Coal Measures, seem to have been made up of trans- 

 ported materials, and were therefore deposited much faster than the limestones, 

 though but few of them appear to have been made with any rapidity. The even- 

 ness of the strata, over a great extent of country, indicates slowness in trans- 

 portation and deposit. The fact, that the materials must have been taken from 

 pre-existing rocks, b}^ the water, before transportation, tends again to convince us 

 of the slowness of their formation. From these considerations, it would not be 

 extravagant to say, that paUeozoic time represents more than one hundred millions 

 of years, and we would close our eyes against the -testimony of the rocks, were we 

 to conclude that palaeozoic time could be estimated by years less than many 

 millions. 



The vegetable kingdom began with the lowest of its. kind, the alga3 or sea 

 weeds, and with the lowest forms of these. The development was as gradual as 

 the deposition of the strata. It was not until the Devonian age, that land plants 

 appeared of sufficient firmness for preseu'vation, if we except Dawson's Psilophyton, ' 

 which probably grew in a marsh. These were of the lowest classes. The}^ be- 

 came more diffuse and diversified with the lapse of time ; but the palaeozoic era 

 closed without the appearance of any of the higher orders or classes. 



The animal kingdom likewise began with the lowest of its kind, the Eozoon 

 canadense. The learned Dr. Haeckel has established the fifth sub-kingdom in 

 animal life to include forms below the RacUata, and therefore very nearly- related 

 to inorganic matter. This sub-kingdom he has called Protista. The Eozoon 

 canadense, under this classification, belongs to the order Polythalamia, sub-class 

 Radiolaria^ class Rhizopoda^ sub-kingdom Protista. Ages passed, about which 

 we know very little, before the period of the St. John's Group, which ushered in 

 the lower Silurian. At this time we find the lowest forms of the Radiates, Mol- 

 lusks and Articulates. The Articulates are represented by the lowest forms of 

 theTrilobites, which, in their perfect state, represented the embryonic condition 

 of the existing Llmulus. Millions of years pass by again, before the appear- 

 ance of Gasteropoda, and Cephalopoda, in the Upper Potsdam Group; meantime 

 the s^'stem of life, which commenced with the lowest forms, as if by spontaneous 

 generation, by evolution, increases species and genera and reaches a higher and still 

 higher grade of development. Later still, in the Calciferous Group, the LainelU- 

 hranchiata commenced its existence; a class that has fought its way through all 

 succeeding time, and is even now in the height of its prosperity and advancement. 

 All classes of life, which existed in the ocean, up to the first appearance of the 

 La7nelUf)ra7ichu(ta^ continued to live, dcA^eloj), increase their species and genera, 

 and improve, through millions of years, before the Vertebrates first made their ap- 



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