INTRODUCTION. 5 



tlie present day a great number of substances are 

 known to possess the same singular property. 



In 1663, the celebrated English chemist Robert 

 Boyle announced to the world that the Diamond 

 possessed the same luminous property as the Bo- 

 logna Stone ; and what we haye just told of Cas- 

 cariolo's labours has its parallel in the discovery 

 of another luminous body, far more remarkable 

 than either. 



In the seventeenth century there lived at Ham- 

 burg an alchemist named Brandt, who having en- 

 deavoured for many years, but in vain, to convert 

 other metals into gold, was struck one day with 

 the golden colour of urine, and doubted not but 

 that this liquid contained some substance that 

 would realize his dreams. Brandt thought that by 

 acting upon the metals he wished to convert into 

 gold with a blackish extract he had prepared by 

 concentrating and evaporating urine, he would 

 certainly operate the desired transmutation. He 

 therefore introduced this black extract into a re- 

 tort with the metals in question, lighted his fur- 

 nace, and watched intently the progress of the 

 operation. The result was negative : the metals 

 after the experiment remained unchanged. How- 

 ever, one evening, after having distilled a consi- 

 derable quantity of urine over some metal or other, 

 and having pushed the distillation as far as pos- 

 sible, he was surprised to find that a peculiar shi- 



