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XVI. Account of the Constituents of various Minerals. By THO- 

 MAS THOMSON, M. D. F. R. S. L. & E. Professor of Che- 

 mistry in the University of Glasgow. 



(Bead Ylth March 1828J 



I HAVE been occupied for about two years past, assisted by the 

 practical pupils in the laboratory belonging to the College of 

 Glasgow, in analysing the most important specimens in my mi- 

 neral cabinet, which seemed to me to require further elucidation. 

 As my practical pupils are seldom fewer than six, and as they are 

 employed the whole day, from nine in the morning till dinner- 

 time, during the whole year, about six weeks in the summer ex- 

 cepted, which I have been in the habit of spending in the coun- 

 try, the number of analyses which has accumulated within that 

 time, has become so great, and some of the results are so curious, 

 that I have selected a few out of the number, for the gratifica- 

 tion of the mineralogical public. It may be requisite to mention, 

 in the first place, that when a pupil comes into my laboratory, the 

 first thing which he does is to transcribe a set of practical rules, 

 which 1 have drawn up for the benefit of my pupils. He is then 

 set to analyse an easy mineral, with the composition of which I 

 am already acquainted. I either shew him myself the different 

 steps of the analysis, or request some of the farther advanced pu- 

 pils to superintend the progress of the analysis, and ensure its 

 accuracy. This method of superintendence is persisted in, till 

 the pupil has familiarised himself with the different steps in the 

 analysis of minerals, and till he has become well acquainted with 

 the appearances of the different precipitates, and knows how to 

 determine the complete separation and the purity of the differ- 



