37^ PHILOSOPHICAL TRANSACTIONS. J[aNNO 1685-6. 



pher Muller, having prepared a precipitate of gold from a solution of this pietal 

 in aqua regis, by means of oil of tartar, and having triturated in a chalcedony- 

 saucer the said precipitate (moistened with water) with some red glass, to be 

 afterwards fused for the purpose of enamelling (according to the directions given 

 by Neri in the 6th book, of his Ars Vitraria) he found, after repeating the tritu- 

 ration a 3d time, that this red powder (which had remained in the vessel for 

 several days) had stained not only the chalcedony-saucer itself (which before 

 was of a pellucid onyx colour throughout) in various places, but the pestle also, 

 and had penetrated so deep (though the substance of the chalcedony was so 

 hard as not to be touched by a file) that the stain could not be got out either 

 by pure water, by lixivia, or by any other liquors ; at the same time the fine 

 polish of the chalcedony was not at all impaired. But when this experiment 

 was repeated with another chalcedony vessel, it did not become coloured like the 

 former. 



A Catalogtie of Simple and Mixed Colours. By R. IValbr. F. R. S. 



N" 179, p. 24. ; ' / 



J, Having sometime since seen a table of the simple colours made use of in 

 limning and painting, I have here endeavoured to give a more philosophical and 

 useful one by the addition of some mixed colours. Not that I pretend to give 

 the shades of all the mixed colours, which are indeed infinite, as the composi- 

 tions and proportions of them may be unlimited ; but I have mixed each of the 

 simple yellows and reds with each of the simple blues, and these mixtures give 

 most of the medium colours, viz. greens, purples, &c. To know what each 

 of these mixed colours is compounded of, you need but look to the top of the 

 table directly over the colour inquired after, where you may find the one ingre- 

 dient, and at the side, in the same row, the other. I expect that this table will 

 be of some use and advantage in the describing of the colours of natural bodies. 

 Thus to describe a plant, it may be seen which of the simple or mixed colours 

 comes nearest to it, and then the word affixed to that colour may be made 

 use of. 



A short Description of the Simple Colours specified in this Table. — 1. Spanish 

 white, made of chalk and alum burnt together. 2. I take the lapis Armenius 

 to be the blue bice sold in the shops, for it is light and friable ; formerly 

 it was brought out of Armenia, but now from the silver mines of Grermany, 

 called Malachites, in high Dutch Bergblaw. 3. Ultramarine is made of 

 the bluest lapis lazuli, which is freest from gold-veins by calcination. 4. Smalt 

 is made of zafFer and pot-ashes, calcined together in a glass-furnace. 5. Litmase, 

 or litmus, I suppose the juice of a plant. 6. Indigo, said by Pliny to be 



