170 Prof. J. C. Bose. On a Self-recovering Coherer and the 



Zinc. — This metal also exhibits moderate sensitiveness j it, however, 

 requires a more careful adjustment. 



Cadmium. — The action of this metal is somewhat similar to that of 

 zinc, but the sensitiveness is very much less. 



Bismuth and Antimony. 



Both bismuth and antimony make very sensitive receivers. Mode- 

 rately small E.M.F. with slight pressure is best suited for these metals. 



Iron and the Allied Metals. 



Iron. — The action of this metal is well known. In one of my experi- 

 ments I used it in connection with mercury. When the contact is 

 very lightly made, there is a tendency towards an increase of resistance 

 by the action of radiation. But after a time the action became normal^ 

 that is to say, there was a diminution of resistance. 



Nickel and Cobalt. — These are also very sensitive. The surface being 

 bright, the E.M.F. and pressure are to be adjusted with some care. 



Manganese and Chromium. — These were obtained in the form of 

 powder. Their action is similar to the other metals of this group. 



Aluminium. — This also makes a sensitive receiver. 



Tin, Lead, and Thallium. 



It is somewhat difficult to adjust tin, but when this is done the metal 

 exhibits fair sensitiveness. Lead is also sensitive. The sensitiveness, 

 of thallium is only moderate. 



Molybdenum and Uranium. 



The specimen obtained was in the form of powder, and very tar- 

 nished in appearance. The sensitiveness exhibited was slight. 



Metals of the Platinum Group. 



Platinum exhibited a moderate amount of sensitiveness. Spongy 

 platinum also showed the same action. The absorption of hydrogen 

 made the action slightly better, but the improvement was not very 

 marked. 



Palladium. — This made a more sensitive coherer than platinum.. 

 The adjustment is, however, more troublesome. 



Osmium. — The specimen was in the form of powder. It requires a 

 higher E.M.F. to bring it to a sensitive condition. The sensitiveness 

 was moderate. 



Rhodium was found to be more sensitive than osmium. 



