con 



[ 108] 



C K 



CO'BXEA. (from cornu, Lat. cornte, 

 Fr. cornea dell'occhio, It.) The 

 anterior transparent portion of the 

 ball of the eye, or that portion of 

 the front of the eye which allows 

 the rays of light to pass through, 

 and permits objects to be reflected 

 on the retina at the back. 



CO'KNEAN. A name applied by De la 

 Beche to designate a variety of 

 Trappean rocks met with in Pem- 

 brokeshire, which rocks may be 

 divided into felspathic, quartzose, 

 and hornblendic, as those minerals 

 prevail in the mass. 



CO'ENEANITB. The name assigned by 

 Dr. Boase to a genus of rocks 

 having a basis of compact felspar 

 combined with hornblende, which 

 latter is generally in a smaller pro- 

 portion than in greenstone. Cor- 

 neanite sometimes contains particles, 

 granules, and minute veins of calc- 

 spar: sometimes it abounds in 

 granules and nodules of quartz : 

 sometimes it contains veins of anti- 

 mony and lead ; but it more 

 abounds in manganese. 



COBNE'LIAN. For an account of this 

 sub-species of calcedony, see Car- 



CO'BNEAN. The name given to a fels- 

 pathic trappean rock. 



COBNEOC/ALCITE. The name proposed 

 by Dr. Boase to be given to a dark 

 limestone, abundantly occurring in 

 Cornwall. It is composed of 

 carbonate of lime, with hornblende 

 and compact - felspar. Of this 

 genus Dr. Boase enumerates six 

 species. 



CO'ENBEASH. A coarse shelly lime- 

 stone ; a provincial term. Corn- 

 brash is a marine deposit, a member 

 of the oolite ; it occurs in Wiltshire. 



CO'RNSTONE. A mottled, red and green 

 limestone, occurring in the old red 

 sandstone. The name of this and of 

 the preceding word may be consider- 

 ed as provincial, and given to them 

 from their presumed utility in 

 producing fertile corn-land. Sir E. 



Murohison has divided what he 

 terms the old red system into three 

 parts, the central of these is the 

 Cornstone Formation. He says 

 "the central masses of this system 

 are chiefly composed of red and 

 green argillaceous spotted marls, 

 affording, on decomposition, the soil 

 of the richest tracts of the counties 



in which it occurs.' 



There 



is no district in which the nature 

 and relations of the cornstone can be 

 better studied than to the north of 

 Ludlow, where this formation 

 occupies a distinct range of hills, 

 rising to the height of four or five 

 hundred feet above the low country, 

 and presenting escarpments to the 

 valley of Corvedale. The spotted 

 marls can never be distinguished 

 from those of the new red sandstone, 

 except, perhaps, when; they are 

 separated from each other by beds 

 of hard, micaceous, sandstone. 

 "Wherever the order of superpo- 

 sition is not apparent, the fragments 

 of fossil fishes which occur in 

 abundance throughout the corn- 

 stones, and which were first 

 detected by Dr. Lloyd, of Ludlow, 

 constitute the best distinction 

 between this formation and the 

 lower new red sandstone, which it 

 so much resembles. These fishes 

 are of very peculiar forms, and 

 their fragments being often of 

 brilliant purple and blue colours, 

 are excellent points of attraction 

 for the eye of the geologist; pre- 

 senting a striking contrast to the 

 surrounding dull red and green 

 matrix in which they are enveloped. 

 The cephalaspis appears to be a 

 characteristic fossil of the corn- 

 stone. 



COENUB'IANITE. (from Cornubia, the 

 Latin name for Cornwall.) Dr. 

 Boase proposes to apply the name 

 of Cornubianite to the rock hither- 

 to distinguished by the name of 

 Killas: he says that the killas 

 appears to constitute a rock sui 



