ART. XIX. Account of the Method of colouring Agates. By 

 JOHN MAcCuLLOCH, M. D. M. G. S. Lecturer on Chemistry 

 to the Board of Ordnance, &c. In a Letter to Dr BREWSTER. 



AN compliance with your request, I here send you the circum- 

 stances which I am able to recollect respecting the colouring of 



* We have just seen a work in two volumes quarto, published at Rio de 

 Janeiro, in 1817, entitled " Corographica Brazilica," certainly the most impor- 

 tant literary production which Brazil has hitherto afforded. It contains a pretty 

 accurate description of the geography of the country, of its various tribes of origi- 

 nal inhabitants, and treats fully of its moral and political condition ; but the na- 

 tural history is considered in a superficial and unscientific manner. ED. 



