COB 



COC 



tom of the crucible ; but the cobalt pro- 

 cured is generally alloyed with arsenic 

 and nickel, and sometimes with other 

 metals, particularly iron. 



A number of the acids oxydise cobalt, 

 and combine with its oxide. The con- 

 centratedsulphuric acid scarcely acts on it 

 in the cold, but when boiled on tiie metal, 

 sulphurous acid gas is disengaged, and a 

 saline matter is obtained, which, when 

 lixiviated, forms a solution of sulphate of 

 cobalt. Nitric acid is decomposed by 

 cobalt, and the metal is oxydized and 

 dissolved. The solution is of a red colour, 

 and by gentle evaporation affords minute 

 prismatic crystals of the same colour, 

 which are deliquescent and decomposed 

 by heat. Muriatic acid does not act on 

 cobalt, but with the assistance of heat ; 

 a small portion oi the metal is then dis- 

 solved. The solution of muriate of co- 

 balt afforus a celebrated sympathetic ink. 

 When much diluted, if letters are traced 

 with it on paper, and allowed to dry, 

 they are invisible ; but when the paper 

 is exposed to a moderate heat, they ap- 

 pear of a lively green : they disappear 

 again when cold, and the experiment may 

 be repeated for any number of times, ta- 

 king care only to avoid too strong a heat, 

 by which they are rendered permanent. 

 The cause of this phenomenon has been 

 ascribed to the muriate of cobalt fixed 

 upon the paper attracting, when cold, 

 moisture from the atmosphere, by which 

 it is, as it were, dissolved, and rendered 

 invisible : when heated, this moisture is 

 evaporated, and the green colour of the 

 salt appears. This explanation appears 

 to be confirmed by the fuct, that the 

 characters are rendered visible by con- 

 fining the paper in a vessel with quick- 

 lime, or sulphuric acid, either of which 

 attracts humidity powerfully . The green 

 colour cannot, however, be ascribed en- 

 tirely to the concentration, but is owing 

 to the temperature ; for the solution itself 

 becomes green when moderately heated 

 in a close phial, and loses this green co- 

 lour as it cools ; nor is it easy to explain 

 bow the temperature does produce this 

 change of colour. 



Cobalt combines with many of the me- 

 tals. Its alloys are generally brittle, and 

 none of them has been applied to any 

 use; nor have they been much examined. 

 The principal, or, indeed, almost all the 

 sole use of cobalt, is in communicating a 

 blue colour to glass, enamel, and por- 

 celain. 



COBBING, in sea language, a punish- 

 ment sometimes inflicted on a Bailor : it 



is performed by striking him a certain 

 number of blows on the breech, with a 

 flat piece of wood, called the cobbing- 

 board. 



COBITIS, the loche,'m natural history, a 

 genus of fishes of the order Abdominales. 

 Generic character: eyes in the upper 

 part of the head ; mouth in the greater 

 number of species bearded ; body almost 

 equally thick throughout, and covered 

 with easily deciduous and small scales ; 

 tail rounded; air bladder hard or osseous. 

 There are five species, of which we shall 

 no' ice : C. barbatula, or bearded loche. 

 This is an inhabitant of the streams of 

 Europe and Asia, and lives upon worms 

 and insects, which it finds on the gravel 

 at the bottom of the water, from which 

 it rarely ascends near the surface. It is 

 extremely prolific,and mt>st highly valued 

 for the table in several places in Europe, 

 where it is cultivated with extreme atten- 

 tion. It dies almost immediately on be- 

 ing taken from the water. To preserve 

 the exquisite flavour of it, it is consi- 

 dered by the dealers in this fish as of 

 great importance frequently to shake Jhe 

 vessel of water in which it is placed. C. 

 fossiiis, or yellow-brown loche. This in 

 habits the stagnant and muddy waters of 

 the midland parts of Europe, and in win- 

 ter completely shelters itself in mud. It is 

 restless before storms,qnitting its retreat, 

 and ranging about in various directions 

 near the surface. When preserved in a 

 vessel of water, with, some earth at the 

 bottom, it invariably indicates the ap- 

 proach of storms by peculiar agitation, 

 and is on this account not unf requently 

 kept to answer the purpose of a baro- 

 meter. 



COCCINELLA, in natural history, a 

 genus of insects of the order Coleoptera. 

 Generic character : antennae subclavated 

 and truncated ; feelers with semi-corclat- 

 ed tip . body hemispheric, with the abdo- 

 men flat beneath. This genus is easily 

 distinguished by its hemispheric form, 

 having the upper parts convex, and the 

 lower flat. The insects of this genus are 

 known by the name of lady-birds. C. 

 septempunctata, or seven-spotted lady- 

 bird, is seen in every garden and field in 

 the summer. It proceeds from a larva 

 of a lengthened oval shape, with a shar- 

 pened tail, of a black colour, varied 

 with red and white specks, and of a 

 rough surface ; it resides on various 

 plants ; and changes to a short blackish, 

 oval crysalis, spotted with red, which 

 gives birth to its beautiful inmate in 

 the months of Mav and June. There 



