20 BLACK, 



discoverer. His features were singularly graceful, full 

 of intelligence, but calm as suited his manner and his 

 speech. His high forehead and sharp temples were 

 slightly covered, when I knew him, with hair of a 

 snow-white hue, and his mouth gave a kindly as well 

 as most intelligent expression to his whole features. 

 In one department of his lecture he exceeded any I 

 have ever known, the neatness and unvarying success 

 with which all the manipulations of his experiments 

 were performed. His correct eye and steady hand 

 contributed to the one; his admirable precautions, 

 foreseeing and providing for every emergency, secured 

 the other. I have seen him pour boiling water or boil- 

 ing 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 adap- 

 tation of the height to the diameter as a necessary 

 condition of success. I have seen him mix two sub- 

 stances in a receiver into which a gas, as chlorine, had 

 been introduced, the effect of the combustion being 

 perhaps to produce a compound inflammable in its 

 nascent state, and the mixture being effected by draw- 

 ing 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 pourtray, the steps by which 

 he made his discoveries, illustrating them with anec- 

 dotes sometimes recalled to his mind by the passages 

 of the moment, and giving their demonstration by 



