PRACTICAL STANDARDS FOR ELECTRICAL MEASUREMENTS. 



51 



APPENDIX IV 



The following table gives the resistance at a temperature of 60° Fahr. 

 (1 5° -55 C.) of a wire of pure annealed copper 1 metre in length, having a 

 mass of 1 gramme, as deduced from the most recent determinations. 



In making the reductions, the values for the temperature coefficient 

 and for the density given by the author, have been used. 



Table (jioing Resistance at 60 Fahr. of a Wire of Pure Annealed Copper, 

 such that 1 inetre iceighs 1 gramme. 



Authority 



Fitzpatrick . 

 Swan and Rhodin 

 Do. (Second sample) 

 Fleming ' . 

 Lasrarde 



Source of Copper 



Electrolytic 

 Swan's Copper 



»» »» 



Swan's Copper 



Grammont Electrolytic 



Reference 



'B. A. Report,' 1890 

 'Proc. R. S.,' 1894 



' Phil. Hag.,' 189.S 

 ' Hospitalier,' 1804 



Mean value 



Value in 

 Ohm 



01475 

 01493 



O-l-ISfi 

 0-1487 

 0-1488 



0-1486 



On the Use of Vectorial Methods in Phi/sics^ 

 By Professor 0. Henrici, Ph.D., F.R.S.' 



[Ordered by the General Committee to be printed in extenso.'] 



Having been engaged for over thirty years in teaching mathematics, 

 chiefly to engineering students, I have always had much sympathy with 

 them. They have to consider mathematics as a tool to help them in their 

 work ; abstract reasoning is in many cases a horror to them. At school 

 they have most likely been treated as duffers, unable to learn mathe- 

 matics ; but if the subject is led up to through concrete examples, every- 

 thing becomes alive and full of interest to them. It is for such men as 

 these that I speak primai-ily, not for mathematicians. It is for them that 

 I advocate the more general use of vectors and their introduction into the 

 school curriculum ; because vectors give the most natural nmtliematical 

 expressions for many quantities in dynamics and physics, and their intro- 

 duction helps in the study of these subjects and in obtaining clear views 

 of the quantities dealt with. 



The very invention of vectors is due to the needs of dynamics, and he 

 who first represented a force by a directed line is their inventor. Who 

 this was seems to be unknown ; Newton was the first who clearly stated 

 the ' Parallelogram of Forces.' Since his time vectors have always been 

 used in dynamics, although the name ' vector ' was only introduced by 

 Hamilton. 



That this representation of a force by a vector is natural no one will 

 dispute, but only the addition of vectors (composition and decomposition 

 of forces) was in use until Hamilton and Grassmann almost simultaneously, 



' In reducing Professor Fleming's result, the density has been talcen as 

 8-91 grammes per c,c. 



