ON STANDARDS FOR USE IN ELECTRICAL MEASUREMENTS. 423 



In the foregoino^ list there are doubtless many inaccuracies and 

 omissions. Although some trouble has been taken to render the list 

 correct as far as it goes, yet it is certainly incomi^lete. It is requested 

 that anyone detecting errors will communicate with some member of the 

 Committee, forwarding the proper correction. The reliance that can be 

 placed on the list will best be indicated by a description of the method 

 employed in compiling it. 



The following periodicals were looked through : ' Philosophical 

 Transactions,' 'Proceedings of the Royal Society,' 'Philosophical Maga- 

 zine,' ' Journal of the Chemical Society,' ' Monthly Notices of the 

 Royal Astronomical Society,' 'Nature,' ' Comptes Rendus de I'Academie 

 des Sciences,' ' Annales de Chimie et de Physique,' ' Berichte der 

 Deutschen Chemischen Gesellschaft,' ' Annalen der Physik und Chemie," 

 ' Beiblfitter zu den Annalen der Physik und Chemie,' ' American 

 Journal of Science and Arts.' In many of these periodicals, abstracts 

 from others, and also references, were found ; the originals of 

 these were then sought and the titles entered in the list. Almost 

 all the references in the third column have been thus verified ; those 

 in the second column (immediately following the titles) have not been 

 verified, but are entered as found in the abstracts. 



Interim Report of the Committee for constructing and issuing 

 •practical Standards for use in Electrical Measurevients, the 

 Committee consisting of Professor G-. Carey Foster, Mr. C. 

 HocKiN, Professor Sir William Thomson, Professor Ayrton, 

 Mr. J. Perry, Professor W. G-. Adams, Lord Rayleigh, Professor 

 F. Jenkin, Dr. 0. J. Lodge, Dr. John Hopkinson, Dr. Muirhead, 

 JNIr. W. H. Preece, and Mr. Herbert Taylor. 



[Plate VL] 



It appeared to the Committee that in order to perform the task 

 entmsted to them, they had two principal questions to consider : First, 

 to select or prepare a well-defined standard of accurately known abso- 

 lute value for each kind of magnitude ; and, secondly, to take measures 

 for making certified copies of each of the adopted standards accessible to 

 the public. 



The standard magnitudes which the Committee have had under 

 consideration as yet are — 



1. The Standard of Resistance. 



2. The Standard of Capacity. 



3. The Standard of Electromotive Force. 



As to the first of these, the standard of Resistance, the Committee 

 were of opinion that, in view of the discrepant results obtained by 

 experimenters who have re-examined the absolute resistance of the B. A. 

 unit, it might be well to reconsider the question whether the ' ohm ' 

 should be defined by reference to a particular coil of wire preserved as a 

 concrete standard, or whether the term ' ohm ' should be understood to 

 mean a resistance of 10^ C. G. S. units. They were also of opinion that 

 it was desirable to continue the experimental investigation of the absolute 

 resistance of the existing standards. 



