COLOURS. 



What is made in England is coarse, rough, 

 gritty ; ana generally has a bluish cast. 



Lamp black is the soot of oil collected 

 by means of inverted vessels placed over 

 the flames ; it is incomparably smooth, 

 and stands well ; but is not very deep. 



Ivory black is made of ivory, bones, 

 Sec. exposed to great heat in a well luted 

 crucible. It is a very deep, but a cold 

 colour. 



Jilue black is made from vine stalks 

 prepared as above : its colour is deep, 

 but with a bluish cast. 



BLUES. 



Indigo is the extract from a plant of 

 that name : it is a cold but permanent 

 colour : it is not miscible with water, but 

 gives way to the sulphuric acid. 



Prussian blue is made with two parts of 

 purified potash well mixed with one of 

 dried bullock's blood levigated : these are 

 calcined in a covered crucible, with a mo- 

 derate fire, until they cease to emit fumes. 



Blue verditer is made by absorbing the 

 copper dissolved in aqua fortis, by aid of 

 whitening. 



Smalt is pounded zaffre, made from the 

 ore of zinc. 



JBrice is levigated smalt, and rather 

 lighter. 



All the above colours are very durable. 



The Crocus-marlis gives a simple pur- 

 ple, which colour may also be obtained 

 from logwood, with a solution of tin. 



GREEKS. 



Verdigris is an incrustation of copper 

 by the corrosion of acids : it is highly 

 poisonous ; but gives a beautiful green 

 colour, with a very slight bluish tinge : 

 when boiled with vinegar, in an earthen 

 vessel, it gives a highly transparent co- 

 lour, fit for washing brass, &c. ; but this 

 is very apt to fade. 



Sap-green is the concreted juice of the 

 buckthorn berry : it is a dull green, and 

 is much in use, though apt to fade. 



WHITES. 



Flake-iolrite is an oxide of lead, formed 

 by corrosion of that metal with vegetable 

 acids. 



White-lead is the same as the above, but 

 coarser ; it is not so good as flake white, 

 nften turning black. 



Pure carbonate of lime stands perfectly 

 well, and is much used : ii is by some 

 called Spanish white, and is nearly the 

 same as the pigments produced from egg* 

 shells, or oyster shells, calcined. 



Calcined hartshorn is an excellent 

 white. 



The above catalogue of colours is in- 

 tended for the service of those who ap- 

 ply them with the brush, as in oil-paint- 

 ing, and in limning. The colours used by 

 dyers are very different, and are chiefly 

 pastil, woad, ancl indigo, for blues ; co- 

 chineal, carthamus, gum-lac, archil, log- 

 wood, madder, &c. for red ; weld, savory, 

 quercitron, fenu-greek, &c. for yellows ; 

 walnut bark, or rind, alder bark, sandal 

 wood, sumach, and soot, are used for 

 browns, or, as they are technically called, 

 fawn colours ; for black, galls, copperas, 

 &c. ; greens are generally compounds 

 made from blue and yellow ; purples 

 from blue and red ; orange colour from 

 red and yellow ; and many shades are 

 made by the mixture of red and black, 

 black and blue, &.c. ; yellow and red also 

 give an olive colour. See DYEIJTG. 



COLOURS diatonic, or musical scale of- 

 In the course of Sir Isaac Newton's ex- 

 periments on the properties of light, he 

 discovered the remarkable fact, that the 

 spectrum of the sun's image, formed by 

 refracted light, let into a darkened room,is 

 longitudinally divided by the points sepa- 

 rating the different colours ; viz. violet, 

 indigo, blue, green, yellow, orange, and 

 red, into spaces, which are respectively 

 equal to . ^. fa _L, .^ ^ and fa 

 parts of the double length of the spec- 

 trum ; as, suppose the spectrum to be 

 360 parts in length, then _8P_ _^ ^ 



Wf<P 7^> and 4 5 o> wi11 represent 

 the length of each colour respectively ,and 

 adding these successively in the reverse 

 order, to ^fo, we have Jffrffl, 



' and 



lowest terms, are 1, J> ff , f, |, |, , |, 

 and 1, and appear to be the diatonic ratios 

 answering to the octave, minor seventh, 

 major sixth, fifth, minor fourth, minor 

 third, major second, and key note. 



From the experiments of Henry 

 Broughton, jun. Esq., " Philosophical 

 Transactions, 1796," it appears that, not 

 only by refraction, but by inflection, de- 

 flection, and reflection, the rays of light 

 may be separated on a chart or screen : 

 and he mentions numerous experiments, 

 wherein the limits of the several colours 

 on the spectrum were carefully marked 



