170 Mr. F. Jenkin on the Question of the 



and weight or section of any reproducing material as the unit of 

 electrical resistance. 



I now come to the third and personal point, and I enter upon 

 it with great regret. I feel that I must have unconsciously 

 written in a manner calculated to give annoyance, or Dr. Siemens 

 could never have accused me of attacking his propositions "in 

 a way not customary in scientific critiques/'' I am the more 

 pained by this, as although I have only a slight acquaintance 

 with Dr. Siemens, I may acknowledge with pleasure the friend- 

 ship of his brother, Mr. C. W. Siemens of London. Certainly, 

 though I have had occasion to differ from Dr. Siemens, and 

 have urged my arguments as forcibly as I could, I never sup- 

 posed that he or any one would have suspected me of " an in- 

 tention to throw a false colouring upon the value of his work ;" 

 indeed I hardly know in what terms I ought to answer such an 

 imputation. 



Meanwhile I prefer to believe that Dr. Siemens will express 

 regret at having in the warmth of controversy made such an 

 accusation'. I myself regret that the Report, which as Secre- 

 tary I had the honour to write and present in 1865, had not 

 been printed before Dr. Siemens wrote his article. The following 

 extract will show the feeling which animated the Committee 

 and myself : — " Thus a difference exists in Dr. Siemens's and 

 Dr. Matthiessen's reproduction of a unit by means of mercury, 

 as pointed out in last year's Report. It is of course probable 

 that differences of this kind will in time disappear, and Dr. 

 Siemens fairly points out that the discrepancy mentioned in last 

 year's Report, between coils made from a very qld and those 

 made from a new determination of the mercury uuit, affords no 

 criterion of the accuracy with which mercury can now be used 

 as a means of reproduction. Dr. Siemens was the first person 

 who produced numerous sets of coils accurately adjusted; and 

 although unable to recommend the adoption of his unit of re- 

 sistance, the Committee once more take an opportunity of ex- 

 pressing their sense of the high value of Dr. Siemens' s researches 

 on the reproduction of units by means of mercury." 



Probably if Dr. Siemens had seen this Report, his article would 

 have been in some respects different. He should remember that 

 if many of our arguments have been directed against his pro- 

 position, there are two good reasons for this, inasmuch as his 

 units alone have been able to challenge any comparison with 

 those of the Committee, and he himself has hitherto alone op- 

 posed our proposals. 



Dr. Siemens refers specially to my Report to the Royal So- 

 ciety on the New Unit of Electrical Resistance. He blames me 

 for using a single determination published in my Report on the 



