2 PROGKESS OF HUMAN KNOWLEDGE. 



has obtained over Matter and its moving Forces, the 

 thought runs back, almost startlingly, to that earlier 

 yet not remote time, when these powers were all 

 hidden from our knowledge as completely as if having 

 no existence in the natural world. In the boyhood of 

 my own life some of them now mightiest in our hands 

 lay dormant and purposeless around us. The period 

 which has disclosed them to our knowledge and senses 

 must ever rank high in human chronology. 



More than sixty years ago Davy showed me, at the 

 Eoyal Institution, the minute globules of sodium and 

 potassium just obtained from the fixed alkalis. In the 

 same laboratory, the birthplace of so many great dis- 

 coveries, I witnessed his first experiments on the 

 chemical actions of the voltaic current an era in 

 chemical science. Very few years later I heard Dalton 

 expound for the first time that Atomic Theory, which 

 (whatever the antecedent suggestions) gave the earliest 

 impulse to those researches, of which organic chemistry, 

 present and prospective, is the most wonderful expo- 

 nent. Yet later, in the theatre of the Eoyal Institu- 

 tion, I was one of a small party to whom Faraday 

 showed the spark he had just succeeded in drawing 

 from the magnet ; so feeble then as to require an 

 effort to see it, but the forerunner of those marvellous 

 powers which have since been elicited from the same 

 source. These dates, though belonging to my own life 

 only, tell in some part what this century has done for 

 physical science. 



In an article of the ' Edinburgh Eeview,' some 

 ten years ago (since republished), I sought to delineate 

 the progress recently made in this great department of 



