COP 



ments, that the conducing power of air is nearly propor- 

 tional to the fifth root of its denfity. Mr. Dalton, however, 

 has rendered it probable, that it varies nearly as the cube 

 root of its denfity. Vapours of all kinds, and every thing 

 that has a tendency to dilate air, diminifli their condufting 

 powers. The conducing powers of common air, oxygen, 

 and azote, as might be expefted, are nearly equal. The 

 conducing power of carbonic acid is rather inferior to that 

 of air, but bodies cool in hydrogen more than twice as faft 

 as in common air ; and Mr. Leflie has endeavoured to fhew, 

 that the adlual condufting power of hydrogen is no lefs 

 than four times greater than that of common air. 



Mr. Dalton's experiments were made with a ftrong phial 

 filled with the gas to be examined, into which he introduced a 

 delicate thermometer through a perforated cube, and ob- 

 ferved the time it took to cool 1 5° or 20°. The following 

 table exhibits the refult of his experiments : 



COOLSPRING, in Geography, a town/hip of Penn- 

 fylvania, in the county of Mercer, having 521 inhabitants. 



COOS, in Ancient Geography. Add — See Cos. 



Coos, in Geography. Add — Coos is a county of New 

 Hampfliire, containing 24townfhips, and 3991 inhabitants. 



COPAL. Add— See Vateria. 



COPPER, in Chemijlry, the name of a metal. Some 

 circumftances omitted in our account of this metal require to 

 be inferted here. 



There are two oxyds of copper, the protoxyd of an 

 orange or red colour, and the peroxyd or black oxyd. 



The protoxyd was obferved byProuft ; butChenevix, who 

 found it native in Cornwall, firft accurately defcribed its 

 properties. It may be formed by mixing together 57.5 

 parts of black oxyd of copper, and 50 parts of copper in a 

 nate of powder, formed by precipitating it from muriatic 

 acid by an iron plate. This mixture is to be triturated in 

 a mortar, and put with muriatic acid into a well-ftopped 

 phial. Potafh dropped into this folution precipitates the 

 oxyd of copper of an orange colour. It may be alfo 

 formed with much lefs trouble by adding excefs of copper 

 to muriatic acid, and letting the whole remain till the green 

 colour difappears, and the folution becomes dark brown and 

 opaque. In this ftate, dirty-white cryftals hke fand are de- 

 poiited. If potafh be added to the brown folution, or a 

 folution of the cryftals above-mentioned, the protoxyd is 

 precipitated in abundance. According to Berzelius, this 

 oxyd is compofed of 



Copper - 100 



Oxygen - 12.5 



Hence the weight of the atom of copper will be 80. 



The peroxyd or black oxyd of copper has been already 

 defcribed. It is compofed, according to Prouft and Ber- 

 zelius, of 



Copper - TOO 



Oxygen - 25 



COR 



Henct the quantity of oxygen in thefe two oxyds is as one 

 to two ; or the protoxyd may be confidcred as compofed of 

 one atom copper and one of oxygen, and the peroxyd 

 of one atom copper and two of oxygen. From thefe de- 

 terminations, the compofition and weights of the atoms of 

 the different falts of copper may be accurately eftimated. 



COPTIS, in Botany, from 'koiHi; to n'/wWf.— Sahfb. Tr. 

 of Linn. Soc. v. 8. 305. De Cand. Syft. v. i. 321. Puirti. 

 390. — Clafs and order, Polyandria Polygynia. Nat. Ord. 

 Ranunculacea, Juff. 



Eff. Ch. Calyx none. Petals five or fix, deciduous. Nec- 

 taries as many, hooded. Follicles membranous, ftalked, 

 beaked, with many feeds. 



1. C trifolia. Three-leaved Coptis. Purfhn. i. — Leaves 

 ternate, obovate. See Helleborus, n. 3. 



2. C. afpIenifoUa. Fern-leaved Coptis. Purfli n. 2 



Leaves twice ternate, pinnatifid. — Found by Mr. Menzies, 

 on the weft coaft of North America, and by Thunberg iu 

 Japan, this being aftually Thaliffrum japonicum of that au- 

 thor, and of Willd. Sp. PI. v. 2. 1303 ! The fiotoen are 

 greenifh. 



CORACHIE, in Geography, a good fea-port in the 

 country of Se'ind ; which fee. 



CORAL, Chemical Properties of. See Vermes. 



CORALLORRHIZA, in Botany, an old name, allud- 

 ing to the branching coral-like form of the root. — Hall. Hift. 

 v. 2. 159. t.44. Brown in Ait. Hort. Kew. v. 5. 209. 

 See Cymbidium. 



Eff. Ch. Lip elongated into a fpur at the bafe. Column 

 unconnedled. Anther a terminal deciduous lid. Maffes of 

 pollen four, oblique. 



We do not doubt the propriety of feparating this plant, 

 and another of American origin, (fee Purfli 593, n. 4.) from 

 Cymbidium ; but we have fome nearly alUed Orchidex from 

 Nepaul, which require to be examined before the limits of 

 Corallorrhi%a can be clearly defined. 



CORDILLERAS. Add— The great body of the 

 Cordilleras, as it extends from Quito northward, approach- 

 ing the gulf of Mexico, and entering the kingdom of New- 

 Granada, is divided into three chains, which are almoft paral- 

 lel, and of which the two lateral branches are covered with 

 fand-ftone, and other fecondary formations, to a very con- 

 fiderable height. The eaftern chain divides the valley of 

 the river Magdalena from the great plains that are drained 

 by the Orinoco and its branches. Inclofed by a circle of 

 mountains belonging to this chain is the high valley of 

 Bogota, the bottom of which is no lefs than 7460 fett 

 above the level of the fea. The waters of this valley are 

 collefted by the fingle ftream of Rio de Bogota, which 

 finds its way through the mountains to the S.W. of the 

 town of Santa Fe : the ftream where it leaves the valley 

 is about 144 feet wide ; it then enters into a rocky channel 

 not more than 40 feet wide, apparently formed, fays M. 

 Humboldt, by an earthquake. From this crevice, the river 

 precipitates itfelf at two bounds to the depth of 574 feet ; 

 and after this fall purfues its courfe to the Magdalena, about 

 ^ miles, ftill defcending with great rapidity, and at the 

 rate of 150 feet to a mile. The natural bridges of Icononzo 

 are on the weftern declivity of this ridge. The central chain 

 is the higheft of the three, and often attains the hmits of per- 

 petual fnow, and greatly furpaffes it in the coIofTal fummits 

 of Guanneas, Baragan, and Quindiu. The weftern chain 

 feparates the valley of Cauca from the province of Choco, 

 and the coafts of the South fea. This is lower than the 

 others, and rifes fo much as it approaches the ifthmus of 

 Panama, that its courfe can hardly be afcertained. In our 



ordinary 



