•S68 Oih the Method of preparing 



fuse that beneficent influence into the atmosphere but 

 at certain determinate seasons, or only when they are 

 green ; these reflections induced me almost to think that 

 it would be necessary to seek for some other constant source 

 oi this vital gas ; I am consequently of opinion, that 

 as nothing in nature is lost, animals themselves may have 

 the means of restoring to the atmosphere that oxygen of 

 ^hich they deprived it. 



Eut this is not the time for entering the field of conjec- 

 ture in regard to this important subject; I shall discuss it in 

 my work on the reepii'ation of men and of animals. For the 

 present I shall tell you that I have finished the composition 

 of four mcniou-s, which will form the first part of my re- 

 searches, and which will soon be published. 



'Xl.ir. A fall Dcscnptinn of the Method of preparing Mr, 

 ■ Geougk Blackman's Superfine Oil-Colottr Cakes; as 

 comnuniicnted to the Society for the Encouragement of 

 Arts, Manuficliires, and Conunerce, a7id practised It/ 

 him in Presence of a Committee appointed hy the Societij 

 to ascertain the Merit of the Invention*. 



X A KE of the clearest gum mastic, reduced to fine powder, 

 four ounces; of spirit of turpentine, one pint ; mix thein 

 together in a bottle, stirring them frequently till the mastic 

 is dissolved : if it is wanted m haste, some heat may be ap- 

 plied ; but the solution is best when made cold. Let the 

 colours to be made use of be the best that can be procured,' 

 taking care that, tn^ washing, 8cc., they are brought to the 

 greatest degree of fineness possible. When the colours are 

 dry, grind them on a hard close stone (porphyry is the best) 

 in spirit of turpentine, adding a small quantity of the mastic- 

 varnish : let the colours so ground become a<rain dry ; then 

 prepare the composition for forming them inlo cakes in the 

 following manner : — Procure some of the purest and whitest 

 sperujaceti you can obtain ; melt it over a gentle fire, in a 

 clean earthen vessel; when fluid, add to it one-third of its 

 weight of pure poppy oil, and stir the whole well together: 

 these things being in readiness, place the stone on which 

 your colrturs were ground on a frame or support, and, by 

 means of a charcoal fire under it, make the stone warm ; 



- * Froqi the twelfth volume of the Transactions of the Society, wh.p 

 vorcd ttie greater si'ver lalcttj and twenty guineas to Mr. BliKkman fop 

 discovering hi', process for ihe use of the public. 



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