356 



a reverse action being observed under certain circumstances with 

 india-rubber, suggested to the author experiments to ascertain 

 whether vulcanized india-rubber stretched by a weight is shortened 

 by increase of temperature. Accordingly, on trial, it was found that 

 this material, when stretched by a weight capable of doubling its 

 length, has that length diminished by one-tenth when its temperature 

 is raised 50 Centigrade. This shortening effect was found to increase 

 rapidly with the stretching weight employed ; and, exactly according 

 with the heating effects observed with different stretching weights, 

 entirely to confirm the theory of Professor Thomson. 



February 5, 1857. 

 The LORD WROTTESLEY, President, in the Chair. 



THE BAKERIAN LECTURE was delivered by MICHAEL FARADAY, 

 Esq., F.R.S., " On the Relations of Gold and other Metals 

 to Light." 



The Lecturer gave an exposition, illustrated by experiments, of 

 the substance of a paper presented by him to the Society under the 

 above title. The following is an abstract : 



The author of this paper hopes that the undulatory theory of 

 light, when more fully and perfectly developed, may aid in comparing 

 local actions with those which take place at a distance, and even help 

 towards the comprehension of the physical means by which the latter 

 are carried on ; and with that view he endeavoured, experimentally, 

 to subject a ray of light to the action of particles, so small in size as 

 to have an immediate and near relation, not only to the undulations 

 of light, but even to the far smaller motions of the parts of the ether, 

 which are supposed to produce, by their joint and successive action, 

 the light-wave. His hope was, that by choosing particles of a fitting 

 substance, experimental results might be obtained which, in the hands 

 of the mathematical philosopher, might aid in perfecting the theory ; 

 and for this purpose gold was selected, because of its high optical 



