[ M4 ] 



to the more perfect knowledge of fleel and iron ores ; that of 

 the difference between barytic and common lime-ftone led to 

 the knowledge of a fubflance that is now a capital inftrument 

 in cheinical analyfis, and evinced the futility of that theory 

 which deduced the origin of all fubftances that burned to 

 lime from fea fhells. The fubftance I now announce to the 

 Academy affords a farther proof of the danger of too ftrid a 

 reliance on general theories, and of the poffibility of detedling 

 many fubftances nearly allied to, but in reality differing from, 

 thofe with which we are already acquainted. It is only after 

 fome years of diligent but fruitlefs refearch after fuch aflimi- 

 lating fubftances that this poJfibiUty may be deemed an Impro- 

 bability. 



The firft account I received of this fubftance, which I fliall 

 call StronthianitCi was from Docflor Crawford in the year 1 790 ; 

 he was fo obliging as to fend me a fpecimen, accompanied, 

 with a letter, informing me that from fome experiments he 

 made it appeared to him to contain a new earth ; what thefe 

 experiments were he did not mention. 



Shortly after, however, it attracted fome attention; in the 

 Miner's Journal of February 1791 a good defcription of its 

 external appearance, and fome account of its chemical proper- 

 ties, are given from the obfervations of Mr. Sulzer. I had. 

 not leifure to examine it until laft Odober ; from the expe-- 

 riments I fince made, in which I was affifted by Mr, Higgins, 

 fuperintendent of our Apothecaries Hall, whofe. chemical abili- 

 ties 



