VII. Chemical Analysis of a Black Sand, from the River 

 Dee in Aberdeenshire ; and of a Copper Ore, from Ar- 

 threy in Stirlingshire. By Thomas Thomson, M. D. 

 Lecturer on Chemistry, Edinburgh. 



[Read ISth May 1807-] 



THE fpecimen which formed the fubjecT: of the firft of the 

 following analyses, was brought from the banks of the river 

 Dee, about feven years ago, by my friend Mr James Mill, who 

 at that time refided in Aberdeenfhire. By him I was informed, 

 that confiderable quantities of it are found in different parts of 

 the bed of that river, — that it is called by the inhabitants iron- 

 sand, — and that they ufe it for fanding newly written paper. I 

 tried fome experiments in the year 1800, in order to afcertain 

 its nature > but was too little fkilled at that time, both in mi- 

 neralogy and practical chemiftry, to manage an analyfis of any 

 confiderable difficulty. 



The black powder is mixed with a good many fmall whitifh, 

 reddifh, and brownifh grains, which, when examined by means 

 of a glafs, prove to be pieces of quartz, felfpar, and mica. From 

 this it would appear, that the fand of the river Dee confifts 

 chiefly of the detritus of granite or gneifs. 



When a magnet is pafled over the fand, fome of the black 

 grains adhere to it, and are by this means eafily obtained fepa- 



I i 2 rate. 



