136 



PLYMOUTH INSTITUTION. 



PROCEEDINGS IN THE ATHEN.IU'M. 



January 8th. — Mr. W. Walker*s Lecture on Geological 

 Changes resulting from Meteorological Agency. 



Resumed from page 90. 



The depths to which man had penetrated below the earth's 

 surface, bore so small a proportion to the distance from the 

 surface to the centre, that all our excavations and mining opera- 

 tions might be considered as so many scratches on the earth's 

 external crust. Those portions of the solid surface that have 

 been examined by geologists, consist of series of layers, or strata, 

 arranged in a certain determinate order which is never inverted ; 

 the lower series being of a somewhat more compact nature than 

 the superincumbent mass. Geologists have classed these 

 successive layers of rocks into three grand divisions, namely 

 primary, secondary, and tertiary formations ; and tliese are 

 again subdivided; the primary formation consists of granite, 

 slate, porphyry, and other hard rocks, traversed by metallic veins, 

 but without any traces of organic remains. The secondary 

 formations rest upon the primary, and consist of sandstone, 

 limestone, clay, coal, iron-stone, chalk, Sec, these strata contain 

 fragments of more ancient strata, corals, marine shells, and 

 bones of animals now extinct. The tertiary series consist of clay, 

 limestone, gravel, sand, alluvion, and vegetable soil ; with petri- 

 fied organic remains of some extinct fishes, animals, and plants, 

 imbedded in the lower members of the series ; and near the 

 surface, remains of amphibia, land and aquatic animals, and 

 plants of the same species, as now occupy the land and water. 

 The lecturer stated, that these organic remains, imbedded and 

 preserved in the different strata of the earth's external crust, 

 formed an authentic and historical record of the different animals 

 and plants that had succeded each other in tiie course of time : 

 and that the different layers of rocks, containing a succession of 

 mineral fragments of more ancient rocks, formed a chronological 

 record of the world, from the period when the secondary rocks 

 began to be formed, up to the present time. Since geologists 

 have begun to register facts, instead of dealing in vague and 

 visionary cosmological specluations, all their researches go to 

 establish the authenticity of the Mosaic account of the creation. 



