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CLYME'NIA. A genus of Ammonites 

 established by Count Munster, (the 

 Endosiphonites of Ansted) distin- 

 guished by having the siphon 

 placed on the ventral margin or 

 close to the body whorls. Morris's 

 catalogue records seven English 

 species from the Devonian system 

 in Cornwall. Lycett. 



CLT'PEIFOEM. Of a shield like shape 

 or form. 



CLY'PEUS. (Lat.) A division of the 

 first class of echinites. The fossil 

 echinites of the second division of 

 anocysti are distinguished as clypei, 

 from their similitude in form to 

 the round bucklers of the ancient 

 foot-soldiers. 



COAL. (col, Sax. kol, Germ, hole, 

 Dutch.) A substance of vegetable 

 origin, composed of charcoal, bitu- 

 men, and earthy matter; the 

 latter forms the ashes which 

 remain after combustion. Common 

 coal is a black, solid, and compact 

 substance, generally of a foliated, 

 or rather laminated, structure, 

 whichjiecessarily directs its frac- 

 ture. Its specific gravity is 

 1-25 to 1-37. It cakes into 

 cinders during combustion in pro- 

 portion to its degree of purity, and 

 the nature of the earths which 

 enter into its composition. Coal 

 has obtained various names from 

 varieties of appearance, hardness, 

 situation whence obtained, &c., &c. 

 The very great improbability of 

 finding good coal above the chalk 

 is now acknowledged by all who 

 have even the smallest acquaintance 

 with the geological relations of the 

 English coal mines. The analysis 

 of coal shews it to consist princi- 

 pally of carbon, hydrogen, oxygen, 

 and nitrogen : a specimen of New- 

 castle coal yielded carbon 75*28, 

 hydrogen 4-18, oxygen 4*58, ni- 

 trogen 15-96. 



COAL FOEMATION-. The carboniferous 

 group succeeds the grauwacke in 

 the ascending series of Europe, and 



is so called because the great mass 

 of European coal is included among 

 the rocks of which it is composed. 

 Considered in its greatest gene- 

 rality? and with reference to where 

 the masses appear in the greatest 

 simplicity, the carboniferous sys- 

 tem consists of three formations, 

 namely, the coal formation, a mass 

 1000 yards or more in thickness, 

 consisting of indefinite alternations 

 of shales and sandstones of different 

 kinds, with about fifty feet of coal 

 in many beds, some ironstone 

 layers, and (very rarely) thin 

 layers of limestone ; mountain lime- 

 stone, a mass of calcareous rocks, 

 from 500 to 1500 feet in thickness ; 

 and old red sandstone, a mass of 

 arenaceous and argillaceous rocks, 

 varying in thickness from 100 to 

 10,000 feet. The coal formation 

 may be understood as applied to 

 the great and principal formation 

 of that mineral, interposed between 

 the newer red or saliferous sand- 

 stone, and the great carboniferous 

 limestone and older sandstone for- 

 mations, or, where these are absent, 

 resting on transition rocks. This 

 is the deposit distinguished by the 

 Wernerians as the independent 

 coal formation. The total thick- 

 ness of coal existing in the English 

 and Scotch fields is generally about 

 50 or 60 feet, divided into 20 or 

 more beds, of a thickness of from 

 six feet to a few inches, alternating 

 with from twenty to fifty or one 

 hundred times as great a thickness 

 of shales and sandstones. Every 

 coal district has its peculiar 

 series of strata, unconnected with 

 any other. A district with its 

 peculiar series of strata is called a 

 coal-field. Coal-fields are of limited 

 extent, and the strata frequently 

 dip to a common centre, being 

 often arranged in basin -shaped con- 

 cavities, which appear to have been 

 originally detached lakes, that were 

 gradually filled up- by repeated 



