President's Address.' 5 



turning-point, or indeed as almost the natal year of chemistry, 

 for on the first day of August of that memorable year, Joseph 

 Priestley discovered oxygen gas — a discovery, as we all know, 

 of the most vital importance, one indeed of such moment at 

 that time, that in the then state of chemical matters, it was 

 absolutely necessary that it should be made in order that the 

 science should be put upon a proper foundation, and should 

 be arrested, so to speak, in its backward course. Previous to 

 the time of Priestley's famous discovery, the most erroneous 

 ideas were entertained regarding the most elementary chemi- 

 cal changes, and although Priestley to the day of his death 

 was a firm believer in the absurd phlogistic theory, he did 

 more than any one else to bring about its destruction, and to 

 pave the way for the entrance of truth where gross error 

 had erewhile reigned supreme. 



Going back some ten centuries from the time of Priestley, 

 we read of a highly cultivated Arabian — who possessed, un- 

 fortunately, a somewhat unpronounceable name, but which, 

 however, has been supplanted by the more manageable one 

 of Geber — who seems to be the first chemical author whose 

 works have, to any extent, been handed down to the present 

 day. Where Geber — who has been called the founder of 

 chemistry — obtained his information, is not very clear ; but 

 wherever it was derived, it was for the eighth century by 

 no means scanty, although it must be admitted that a great 

 deal of error was intimately alloyed with the grains of truth 

 which he possessed. Thus he was tolerably well acquainted, 

 in some respects, with the metals — gold, silver, copper, iron, 

 tin, lead, and mercury ; but he regarded the first six of these 

 as being compounds of mercury and sulphur in different 

 proportions. Gold and silver, he said, contained more pure 

 mercury than the others, and in that way he explained the 

 different behaviour of these two metals, and that of the 

 others when exposed to heat. These two — the gold and 

 silver — he affirmed remain unchanged in the fire in conse- 

 quence of so much of the pure metallic quality entering into 

 their composition ; while the others, as they contain more 

 sulphur and impure mercury, are readily affected by heat. 

 He was also of opinion that the baser metals might, by 



