46 SCIENCE 



described. Principal Griffiths, in a recent 

 lecture, recounts a Cambridge experience. He 

 had been explaining to some pupils the laws 

 of floating bodies and asked one of them to 

 come to his laboratory in the afternoon and 

 verify what he had been told. The man 

 looked up with mild surprise and asked, "Do 

 you mean to say this really comes off?" 

 Teaching by experiment was clearly necessary. 

 Laboratory notebooks were written. In 

 due course (in 1885) Glazebrook and Shaw's 

 Practical Physics appeared, and I am glad to 

 say after over 30 years of life is vigorous still. 

 It has been followed by many similar books 

 and has, I trust and believe, done much useful 

 and important work. A man who is to de- 

 velop into a physicist must have an intimate 

 knowledge of the existing methods of physical 

 investigation. Measurement is so important 

 a factor in many branches of knowledge that 



