PROCEEDINGS 



OF 



THE ROYAL SOCIETY. 



February 1, 1883. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " On the Electrical Resistance of Carbon Contacts." By 

 Shelford Bid well, M.A., LL.B. Communicated by Pro- 

 fessor W. G. Adams, F.R.S. Received January 18, 1883. 



1. Object of the Investigation. 



It is well known that the electrical resistance of carbon contacts 

 diminishes with increased pressure, though, so far as I am aware, the 

 phenomenon has never hitherto been systematically investigated. 

 The experiments described in this paper were begun with the object 

 of establishing a quantitative relation between pressure and resist- 

 ance ; but the subject grew considerably under treatment ; fresh facts 

 from time to time claimed attention, and several interesting details, 

 not, I believe, previously observed, were eventually bronght to light. 



Loose contacts are proverbial for the nncertainty of their action, 

 and it was to be expected that the investigation would prove trouble- 

 some and the results obtained by no means uniform. By multiplying 

 experiments, however, the element of uncertainty was to a great 

 extent removed, and in most cases it was found possible to indicate a 

 general law with tolerable certainty. 



2. Apparatus for Regulating Pressure. 



The instrument used for regulating the pressure is shown in fig. 1. 

 vol. xxxv. B 



