CL A 



CLE 



rous insects, of the section Heteromera 

 and subsection Stenelytra, named from 

 the genus cistela. 



CI'TRATE. A salt formed by the com- 

 bination of citric acid with a base. 



CI'TRENE {citrus, a lemon). A pe- 

 culiar carburetted hydrogen, constituting 

 the principal part of the volatile oil of 

 lemons. 



CITRIC ACID {citrus, a lemon). The 

 acid of limes, lemons, &c. By exposure 

 to heat, it is decomposed, with the forma- 

 tion of the pyro-citric and citricic acids. 



CLADE'NCHYMA (K\a3or, a branch, 

 ^YXi'M"* infusion). A modification of the 

 parenchyma of plants, characterized by 

 its branched form. 



CLADO'CERA. An order of the bran- 

 chiopodous Crustacea, in which the cara- 

 pace is formed like a bivalve shell, and 

 there are five pairs of thoracic members. 

 A characteristic example occurs in the 

 daphnia pulex, or water-flea. 



CLAIRVO'YANCE. Clearsightedness; 

 a peculiar mode of sensation, or second 

 sight, connected with somnambulism, and 

 supposed to be diffused over the whole 

 surface of the body, but to be especially 

 seated in the epigastrium and fingers' 

 ends. 



CLARIFICATION {clarus, clear, fio, 

 to become). The process of clearing 

 liquids, by subsidence of the suspended 

 particles, and decantation of the super- 

 natant liquor; by filtration through 

 porous substances ; or by coagulation, or 

 the admixture of albumen, and the sub- 

 sequent action of caloric, acids, &c. 



CLA'VATE {clavus, a club). Club- 

 shaped ; a form in which one extremity 

 is slender and pointed, while the other is 

 thick and obtuse, as in many of the zoo- 

 phagous mollusca; in filaments, styles, 

 and the vittae of umbelliferous plants. 



CLAVICO'RNES {clavus, ?Lchxh, cornu, 

 a horn). A family of the pentamerous 

 Coleoptera, characterized by the club- 

 shaped form of the extremities of the 

 antennae, the terminal points frequently 

 forming a club. 



CLAW OF PETAL. The narrow part 

 at the base of some petals, which is ana- 

 logous to the foot-stalk of a leaf, as in 

 the pink. 



CLAY. An argillaceous rock, of an 

 unctuous, soft, friable, and dense homo- 

 geneous texture, forming a tenacious 

 paste with water, and of various colours. 

 The varieties of clay are essentially sili- 

 cates of alumina. 



1. Indurated Clay is a variety of trap 

 80 



rocks, with a dull earthy fracture, vary- 

 ing in colour from greenish-grey to grey- 

 ish-white, or red, or brown, or even 

 black. 



2. Kimmeridge Clay is a subdivision of 

 the Upper Oolite Formation, of a blue 

 or yellowish colour, more or less slaty or 

 passing into slate, sometimes so impreg- 

 nated with bitumen as to be used for 

 fuel, and containing remains of saurian 

 reptiles and shells. 



3. Oxford Clay, or Clunch Clay, is also 

 a subdivision of the Middle Oolite Forma- 

 tion, of a dark blue colour ; some of the 

 beds are bituminous, and aliiound in sep- 

 taria, or masses having internal dissepi- 

 ments. In its lower part are beds of 

 Kelloway rock, calcareous grit or sand- 

 stone, coral rag and oolite, and calcareous 

 sandstone. 



4. Weald Clay. The upper portion of 

 the Wealden Formation, composed of 

 beds of clay of a bluish or brownish 

 colour, sandstone, calcareous sandstone, 

 conglomerate, limestone, and iron-stone. 

 The mass contains scales of mica, iron- 

 pyrites, crystals of selenite, and traces of 

 lignite. 



CLAY IRON-ORE. One of the ferri- 

 ferous rocks from which iron is procured 

 in great abundance. It is of an earthy 

 aspect, with an even or conchoidal frac- 

 ture, yellow streak oi powder, and dull 

 colours. 



CLAY SLATE. By this name different 

 rocks have been designated. 1. A mica- 

 ceous rock is so named, appearing to be 

 mica-slate in a state of extreme division, 

 the scales of mica having gradually be- 

 come so attenuated, as to give it a homo- 

 geneous, glistening appearance. 2. A 

 more extensive series of strata of clay- 

 slate is found associated with grey-wack6 

 and other rocks of a less crystalline tex- 

 ture than the primary, and occurs in the 

 Cumbrian and the Cambrian Groups of 

 rocks. 



CLAYSTONE. Compact felspar, with 

 an earthy aspect, conchoidal uneven frac- 

 ture, and of various colours. It is often 

 porphyritic, containing crystals of felspar. 

 It occurs in veins, as well as in mountain 

 masses. 



CLEAVAGE. The mechanical divi- 

 sion of crystals, by which the inclination 

 of their lamina: is determined. 



Certain rocks, usually called slate- 

 rocks, admit of being cleaved into an in- 

 definite number of thin laminae which 

 are parallel to each other, but which aro 

 generally not parallel to the planes of the 



