LORD KELVIN 95 



safe as long as it was in his hands, it was impossible for 

 him to deposit it on the table without running the risk of 

 an inconveniently heavy shock. Finally, after rapid de- 

 liberation, two of us held a towel by its corners, and Sir 

 William dropped the jar safely into the middle ; it was 

 then possible to touch the outside without mishap. In 

 short we had little systematic teaching, but were at once 

 launched into knowledge that there is an unknown region 

 where much is to be discovered ; and we were made to 

 feel that we too might help to fathom its depths. 

 Although this method is not without its disadvantages 

 for systematic instruction is of much value there is much 

 to be said for it. On the one hand, too long a course of 

 experimenting on old and well-known lines, as is now 

 the practice among teachers of science, is likely to imbue 

 the young student with the idea that all physics consists 

 in learning the use of apparatus, and in repeating 

 measurements which have already been made. On the 

 other hand, too early attempts to investigate the unknown 

 are likely to prove fruitless for want of manipulative skill, 

 and for want of knowledge of what has already been 

 done. The best of all possible training, however, is to 

 serve as hands for a fertile brain the brain of one who 

 knows what he wishes to discover, who is familiar with all 

 that has already been attempted, and who gradually trains 

 his assistant to take part in the thinking as well as in the 

 manipulation. If at the same time the student is made 

 to read, not merely concerning the problem on which he 

 is immediately engaged, but on all branches of his sub- 

 ject, nothing can be better than such stimulating inter- 

 course with an inventive teacher for those who have ability 

 to profit by it. 



It is extremely difficult to explain Lord Kelvin's contri- 

 butions to knowledge to those who have not themselves 

 some acquaintance with its problems. Let me begin by a 



