Oct. 1, 1S70.] 



HARDWICKE'S SCIEN CE-GOSSIF. 



217 



TEE STOBY OF A PIECE OE LIMESTONE, 



By J. E. TAYLOR, E.G.S. 



AM elected as 



spokesman for 



a common and 



well-known min- 



neral, which is 



abundant in 



every geological 



formation. Our 



age, therefore,varies as greatly 



as it is possible for mundane 



time to allow. Chemically, 



our composition is always 



pretty much the same, being 



merely carbonate of lime. 



In all the rock formations 

 we are further distinguished 

 from the sandstones, shales, 

 and conglomerates, by our 

 being almost wholly of vital 

 origin, that is, manipulated 

 through the agency of living 

 forms. Whereas the other rocks I have mentioned 

 are the result of mechanical forces, wearing down 

 and triturating pre-existing rocks, and then re- 

 depositing the debris along old sea-bottoms. In 

 consequence of this difference, the geologist finds 

 in us by far the greater number of those organic 

 remains, especially of marine animals, by whose aid 

 he is enabled to sketch forth the development of 

 the world's great life-plan. 



As a rule, all limestones have been deposited, as 

 fine calcareous ooze, away out in deeper water; con. 

 sequentiy the circumstances have been doubly 

 favourable for the preservation of any animals which 

 might have died and become entombed in this limy 

 mud. 



The more boisterous conditions which prevailed 

 in the shallower waters, where coarse sands and con- 

 glomerates were formed, prohibited such favourable 

 preservation. At the same time, with the exception 

 of what are known as freshwater limestones (which 

 bear a very small ner-centage to the other rocks of 

 No. 70. 



the earth's crust), I must acknowledge that the 

 sandstones afford most valuable evidence of the 

 terrestrial animals. This, as might be expected, is 

 mainly owing to the fact that the latter were formed 

 nearer to the shore, so that carcasses of land animals 

 accidentally drowned or carried into the sea by 

 rivers watering large islands or continents where 

 they lived, would sink to the bottom, and be buried 

 up in coast deposits ; whilst the sandstone and 

 shale formations testify to the long-continued wear- 

 and - tear of the solid land by meteorological 

 agencies : therefore, the limestones bear out the 

 idea of our planet's antiquity, by suggesting the 

 immense lapse of time which must have occurred 

 whilst simple and lowly animal functions were 

 elaborating the greater proportion of all the lime- 

 stone rocks. 



But I intend to let each of these speak for itself. 

 They are of age, ask them ! Each contains its own 

 suite of organic remains, the extinct creatures 

 which lived and died whilst the limestone mass 

 was slowly accumulating as calcareous ooze. They 

 are tombs of the forgotten dead — stony scrolls, 

 written within and without ! 



I myself belong to that most interesting geologi- 

 cal formation known as the Silurian. Away in the 

 heart of the "Black Country," where no less than 

 thirty feet of solid coal abuts against their flanks, 

 you may see cropping up an irregular and continuous 

 ridge of limestone hills. It is theDce I am derived. 

 You may gather some idea of the forces which 

 slowly upheaved these strata by seeing the steep 

 angle at which they lie : a little more and they 

 would have been quite perpendicular. But this 

 upheaval was not violent or sudden ; oil the con- 

 trary, I distinctly remember its operating through 

 long - continued ages subsequent to the Silurian 

 period. The process was so slow as to be almost 

 imperceptible, for Nature knows little or nothing 

 of those violent cataclysms which have been so 

 foolishly ascribed to her ! Examine the steep 

 flanks of the Wren's Nest, near Dudley. There is 



L 



