32 PETER GUTHRIE TAIT 



and galvanometer." Sir William soon appeared, and we were immediately 

 commandeered into his service. And then followed the wildest piece of 

 experimenting I ever had the delight of witnessing. The Gramme machine 

 was run at various rates with various resistances introduced, and simultaneous 

 readings of the quadrant electrometer and a shunted mirror galvanometer 

 were taken. The electrometer light-spot danced all over the scale, and 

 I had to bring it to reason by frequent changes in its sensitiveness 

 demanding a continual retesting with a standard cell so as to be able to 

 reduce to the same scale. Full of impatience and excitement Thomson 

 kept moving to and fro between the slabs on which the instruments stood, 

 suggesting new combinations and jotting down in chalk on the blackboard 

 the readings we declared. Tait stood by, assisting and at the same time 

 criticising some of the methods. At length Sir William went to the further 

 side of the lecture table and copied into his note book the columns of 

 figures on the blackboard. After a few hasty calculations he said : 

 " That will do, it is just what I expected." Then off he hurried for a 

 hasty lunch at Tail's before the start for London where during the next 

 week he was to give expert evidence in a law case. As they withdrew 

 Tait looked back at us with a laugh and said " There's experimenting for 

 you ! " Early on Monday morning we were startled by a message from 

 Tait who had just received a telegram asking for the numbers on the 

 blackboard. Thomson had mislaid his note book ! Also the original record 

 had been obliterated ! Fortunately for a man of Thomson's profound 

 physical intuitions the loss would not be irreparable. He had in fact 

 tested his theory as the experiments were in progress. 



Tait's official position combined with his high reputation as mathe- 

 matician and physicist brought him into touch with many of the great 

 scientific men of the day. More especially was his verdict on questions 

 of scientific history regarded with interest and respect, in spite of the fact 

 that in several instances his views and those of his correspondents diverged 

 considerably. I have quoted in a later chapter from both Helmholtz and 

 Verdet in illustration of this point. 



Many instances are to be found in his correspondence expressive of 

 the esteem in which he was held by his contemporaries on the Continent 

 of Europe. The letters display a friendliness of tone and a frankness of 

 utterance which show that the writers, one and all, recognised his unfailing 

 honesty of purpose and looked upon him as one whose opinion was worth 



