CO A 



coc 



horizontal base ; and the stratus, or fall- 

 cloud, spreading horizontally in a con- 

 tinuous layer, and increasing from below. 

 Tbe first of these forms is confined chiefly 

 to the higher regions of the atmosphere ; 

 the second occupies a lower, but still an 

 elevated station ; the third usually rests 

 upon the surface of the earth, constitut- 

 ing mists, 



2. Modifications. Of the four modified 

 forms of clouds, two are intermediate, 

 and two are composite. 1. The inter- 

 mediate forms are the cirro-cumulus, 

 consisting of small, roundish, and well- 

 defined masses in close horizontal ar- 

 rangement ; and the cirro-stratus, like- 

 wise in small and rounded masses, but 

 attenuated towards a part, or towards the 

 whole, of their circumference. 2. The 

 composite forms are the cumulo-stratus, 

 made up of the cirro-stratus blended with 

 the cumulus, the cirro-stratus being 

 either intermingled with the larger 

 masses of the cumulus, or widely en- 

 larging the cumulous base ; and the 

 cumulo-cirro-stratus, nimbus, or rain- 

 cloud, being a horizontal layer of aque- 

 ous vapour, over which clouds of the 

 cirrous form are spread, while other 

 clouds of the cumulous form enter it 

 laterally and from beneath. 



CLOVES. A technical appellation of 

 the small bulbs developed at the base of 

 a parent bulb. 



CLUPE'IDiE. The Herring tribe; a 

 family of Malacopterygious or soft-spined 

 fishes, named from the genus Clupea, 

 and differing from the Salmonidae in the 

 absence of fatty matter in the dorsal 

 fin. 



CLY'PEIFORM {clypeus, a shield, 

 forma, shape). Shield-shaped; a term 

 applied to the large prothorax in beetles. 

 Clypeate is a similar term, applied, in 

 Botany, to the scales found on the leaves 

 of certain plants, and synonymous with 

 scutate or scutiform. 



COAGULA'TION {con and agere, to 

 bring together). A term formerly syn- 

 onymous with crystallization, but now 

 applied to the partial solidification of a 

 fluid body by exposure to cold, or by the 

 addition of some agent. Spontaneous 

 coagulation denotes the cohesion of the 

 particles of the blood, of some effused 

 fluids, &c. Induced coagulation denotes 

 the effect produced upon albumen by 

 heat, alcohol, acids, rennet, &c. 



COAL. A combustible mineral, con- 

 sisting of bitumen, carbon, and earthy 

 matter, in various proportions. The 



varieties are easily recognized, being 

 hard, black, brittle, and laminated. Peat, 

 which consists of partially decomposed 

 roots and stems of various plants, may 

 be considered as forming one extremity 

 of the series, which terminates in the 

 other with glance coal or anthracite. 



COAL FORMATION. A term gene- 

 rally employed as synonymous with that 

 of coal measures or carboniferous group. 

 This very comprehensive group embraces 

 not only the coal strata, and the beds of 

 sandstone, limestone, and others alter- 

 nating with it, but the mountain lime- 

 stone and the old red sandstone, on which 

 the proper coal group may be said to 

 rest. 



Werner's Coal Formations. The first 

 or oldest is called the independent forma- 

 tion, from the individual depositions 

 composing it being independent of, and 

 unconnected with, each other. The se- 

 cond occurs in the newest floetz-trap 

 formation ; the third in alluvial land. A 

 fourth would comprehend peat and other 

 similar substances. 



COAL GAS. A gas procured from 

 coal, when subjected in close vessels to 

 a red heat, and employed for illumi- 

 nation. 



COA'RCTATE {coarcto, to compress). 

 An epithet applied to the pupa of an in- 

 sect, which is enclosed in a case, giving 

 no indication of the parts contained in it. 



COARSE COAL. A sub-species of 

 black coal, occurring in the German coal 

 formations. To this head is also referred 

 the soot coal, which occurs together with 

 slate-coal, in the Forth district, &c. 



COATING. Loricaiion. A method of 

 securing or repairing retorts used in dis- 

 tillation. Coatings are made of marly 

 earth, kneaded with fresh horse-dung, 

 slaked lime, and linseed oil, &c. 



COBALT {Cobalus, the demon of 

 mines). A metal, found chiefly in com- 

 bination with arsenic, as arsenical co- 

 balt; or with sulphur and arsenic, as 

 grey cobalt ore. These ores are em- 

 ployed to give the blue colour of por- 

 celain and stone- ware. 



CO'BALUS. The demon of mines, 

 which obstructed and destroyed the 

 miners. The Germans formerly used a 

 form of prayer for the expulsion of the 

 fiend. The ores of cobalt, being at first 

 mysterious and intractable, received their 

 name from this personage. 



CO'CCIDiE (coccus, the cochineal in- 

 sect). The Scale insects ; the single 

 family of the monomerous Homoptera, 



