186 



RESEARCH 



and methods of comparing resistances devised ; 

 Matthiessen investigated the properties of materials 

 suitable for these standards, and Thomson developed 

 a number of the instruments known by his name. 



It had become possible to measure the forces 

 arising from electrical actions and to predict the 

 effects which would be produced from currents cir- 

 culating in conductors, and though much remained 

 to be discovered the path of discovery was found 

 and the consequences of advance along that path 

 were certain. They are seen in the importance of 

 electricity in the world to-day, and it is to the 

 pioneer work of the committee that they are due. 

 The committee was dissolved in 1870. Meanwhile 

 experiments in Germany and America had led to 

 some doubt as to whether the standard resistance 

 of the committee (the British Association unit, as 

 it came to be called) represented the ohm one 

 thousand million absolute units of resistance with 

 all the accuracy possible. In consequence, on the 

 suggestion of Ayrton, the committee was re-appointed 

 in 1881. Thenceforth Rayleigh took a leading part 

 in its deliberations. As the consequence of its work 

 the fundamental standards were determined with 

 an accuracy of a few parts in ten thousand ; and 

 this led in 1890 to the appointment of the Board of 

 Trade committee on standards for the measurement 

 of electricity for use in trade. As a result the 

 standards recommended by the Association committee 

 became the legal standards for the Empire. After 

 some further discussion and experiments, an Inter- 

 national Congress of Electricians met in London in 

 1908 with Rayleigh as president, and the standards, 

 with some trivial modifications, were accepted as 



