352 ABSTRACTS OF SCIENTIFIC PAPERS 



Professor Jenkin as a member of the British Association Committee on 

 Standards of Electrical Resistance, 1862-1869. Besides taking an 

 active share in the classical experiments of the Committee, which esta- 

 blished the absolute system of electrical measurements as a practical 

 method and fitted it for general adoption, Professor Jenkin, as the 

 Committee's Secretary, drafted the Reports, and afterwards edited a 

 volume in which they were republished, 1 along with Articles XIII. 

 and XX. below. The following articles are parts of the Reports 

 with which his name is specially connected. 



IX. Appendix H to the First Report of the Committee on Electrical 

 Standards. f Description of the Electrical Apparatus arranged 

 by Mr. Fleeming Jenkin for the Production of exact Copies of the 

 Standard of Resistance.' ' British Association Report for 1862 ; ' 

 Reprint, p. 35. 



The apparatus is a modification of Wheatstone's Bridge in which 

 the two arms forming the ' ratio ' of the bridge are made adjustable 

 by connecting them through a short length of wire furnished with a 

 sliding contact. The two portions into which the contact piece divides 

 this resistance of the wire supplement, respectively, the resistance 

 coils of the two arms of the bridge which form the ' ratio.' Provision 

 is also made for interchanging the known and unknown resistance 

 in the other two arms of the bridge, so as to eliminate error due to 

 inexactness in the ratio a process analogous to double weighing in 

 the use of a balance. The apparatus includes a key which closes 

 first the battery circuit and then the galvanometer circuit by a single 

 motion of the finger. [The arrangement of bridge described in this 

 paper is discussed in Maxwell's ' Treatise on Electricity,' vol. i. 350.] 



X. Appendix C to the Second Report of the Committee on Electrical 



Standards. ' On the Elementary Relations between Electrical 

 Measurements.' By Professor J. Clerk Maxwell and Mr. Fleem- 

 ing Jenkin. 'British Association Report for 1863,' p. 130 ; Re- 

 print, p. 59 ; ' Philosophical Magazine,' 1865, vol. xxix. 



This important paper forms a concise and comprehensive treatise 

 on Absolute Magnetic and Electric Units and the theory and methods 

 of electrical measurements. Its scope is best shown by the following 

 Table of Contents : 



1 Reports of the Committee on Electrical Standards appointed by the 

 British Association for the Advancement of Science. Edited by Professor 

 Fleeming Jenkin, F.R.S. E. & F. N. Spon: London and New York, 1873. 



