1821.] Production of Colours bi/ Mechanical Division. 183 



ther one part of metallic gold with 20 parts of common enamel- 

 lers' flux, and obtained a rose-coloured enamel without the 

 slightest metallic appearance. The gold was easily ground as it 

 was in that friable state, to which it is reduced by some process 

 with which I am unacquainted, and now commonly sold by the 

 refiners. As the above experiment shows that metallic gold is 

 capable of imparting a rose colour, it is natural to conclude that 

 in all other cases, the colour is in reality owing, not to the 

 oxide, as usually stated, but to metallic gold in a state of minute 

 subdivision. 



( The above result inclined me to form the same inference, with 

 respect to the enamel colours which may be obtained from 

 platina, and to suspect that the beautiful black * described by 

 Mr. Cooper in the Journal of the Royal Institution, No. V.is, in 

 fact, owing to minutely divided platina in the metallic state. I, 

 therefore, mixed three parts of flux with one part of the deep 

 black powder, described in the same paper, as a hydrate of pla- 

 tina, in the hopes of producing the same rich black colour, but I 

 obtained only an enamel of a dark grey colour much like plum- 

 bago. This result was certainly contrary to my expectation, and 

 would lead to the conclusion that oxygenation of the platina is 

 necessary to produce a fine black, but I do not think the expe- 

 riment decisive, and hope that further trials will enable me to 

 speak with more certainty. I am, Sir, 



Your most obedient servant, 



J. P. Charlton. 



Article IV. 



On the Lacerta Gigantea of the Ancient World. 

 By S. T. Von Sbmmering.t (With a Plate.) 



[This paper was recommended to the Editor's notice, and lent 

 to him for translation, by his friend Mr. Parkinson, author of the 

 " Organic Remains."] 



Bavaria, a country which possesses such a number of the 

 finest remains of a former world, is now able to show also those 

 of that wonderful monster, of which hitherto no traces have been 

 discovered, except in the environs of Maestricht and Vicenza, 

 the same animal concerning which, in 1812, Cuvier % said, "La 



• The same black enamel may be obtained by boiling insoluble muriate with caustic 

 potash. 



+ Read June 25, IS 1 6, at the Royal Academy of Sciences. 



* Recherches sur lcs Ossemens Fossiles de Quadrupedes, torn. iv. Paris, 1812. 

 Prcf. p. 5. Sec also my treatise on the Crocodilua Priscus, or the Gavial of Antiquity, 

 in the Memoirs of the Royal Academy of Sciences, Sect. 21 and 2"?. 



