151 



Mr. F. H. Nalder observed that the 

 insulation resistance between the primary 

 and secondary coils was important in the 

 transformer. It was also of very great 

 moment to apparatus in houses, which, if 

 the insulation should break down, would 

 be liable to cause fire. That in a meas- 

 ure was looked after by most makers, 

 who provided covers for the transformers. 

 Engineers should come to the same con- 

 clusion with respect to the minimum insu- 

 lation resistance between primary and 

 secondary coils, and also between the 

 primary coils and the frame.. 



Professor W. E. Ayrton remarked that 

 although some points in the paper might 

 be not quite right, it was of a highly 

 suggestive character. He wished to 

 follow those who had preceded him in 

 condemning the expression " mean elec- 

 tromotive force " employed in the paper. 

 The expression had now a perfectly 

 definite signification in connection with 

 alternate-current circuits; it was, there- 

 fore, a mistake to use it as a substitute 

 for another expression which had also a 



