BLACK. 347 



which all the manipulations of his experiments were 

 performed. His correct eye and steady hand contri- 

 buted to the one ; his admirable precautions, foreseeing 

 and providing for every emergency, secured the other. 

 I have seen him pour boiling water or boiling acid 

 from a vessel that had no spout into a tube, holding it 

 at such a distance as made the stream's diameter small, 

 and so vertical that not a drop was spilt. While he 

 poured he would mention this adaptation of the height 

 to the diameter as a necessary condition of success. I 

 have seen him mix two substances in a receiver into 

 which a gas, as chlorine, had been introduced, the effect 

 of the combustion being perhaps to produce a com- 

 pound inflammable in its nascent state, and the mixture 

 being effected by drawing some string or wire working 

 through the receiver's sides in an air-tight socket. The 

 long table on which the different processes had been 

 carried on was as clean at the end of the lecture as it 

 had been before the apparatus was planted upon it. 

 Not a drop of liquid, not a grain of dust remained. 



The reader who has known the pleasures of science 

 will forgive me if at the distance of half a century I 

 love to linger over these recollections, and to dwell 

 on the delight which I well remember thrilled me 

 as we heard this illustrious sage detail, after the 

 manner I have feebly attempted to pourtfay, the steps 

 by which he made his discoveries, illustrating them 

 with anecdotes sometimes recalled to his mind by 

 the passages of the moment, and giving their de- 

 monstration by performing before us the many expe- 

 riments which had revealed to him first the most 

 important secrets of nature. Next to the delight of 



