Changes yi'oduced in Matter hy Electric Wa ves, 



465 



should be no jarring motion, as mechanical disturbance was found to 

 break up the complex atomic aggregation in the radiation product. 

 During eight minutes of exposure the receiver continued to exhibit an 

 increase of resistance, after which the substance became positive, being- 

 converted to the B state ; this positive state lasted for a minute under 

 exposure to radiation, then there was a reversal to the original nega- 

 tive state — as if the structure so laboriously built up suddenlj^ gave 

 way. Subsequently there were series of reversals, the specimen 

 becoming more and more inert, and, after an exposure of about thirty 

 minutes, the sensitiveness was practically lost. 



The curve given below represents approximately the results of the 

 experiment. During certain periods the substance became so nearly 

 neutral that it was difficult to interpret whether the substance was 

 positive or negative. The lower halves of the curve represent the 

 negative and the upper halves the positive states, and the correspond- 

 ing numbers represent, in minutes, the duration of these states. 



^' 3' /' 



yiyiuzyi^ 



a' 4' 3' 5' /' 



Fig. 1. — Electric Keversal Curre. 



[Eadio-molecular Oscillation . 



It was said that, owing to molecular reversals due to radiation, 

 there should be a corresponding series of electric reversals. In this 

 investigation it is essential that the substance examined should be 

 completely protected from all disturbances, such as mechanical vibra- 

 tion, &c., and only subjected to the action of radiation. The experimen- 

 tal difficulties are very great. If we take a strongly sensitive positive 

 substance — say iron, the effect of the first flash of radiation (a diminu- 

 tion of resistance) is very great, and the subsequent relatively feeble 

 reversal effects, unless carefully looked for, are liable to pass unnoticed. 

 After the first adjustment, the receiver should on no account be 

 touched, as mechanical jars are found to undo the effect of radiation. 

 Though by special care the mechanical jars could be reduced to a 

 minimum, yet it appeared advisable to devise appropriate means 

 by which the necessity of touching the receiver for subsequent adjust- 

 ments is altogether avoided. The method adopted to this end varies 

 with individual (3ases. In the case of arsenic, for example, the 

 action of radiation is often to produce a very great increase of 

 resistance, and thus convert the substance into a non-conductor. 

 The pressure has therefore to be so adjusted at the beginning, that 

 the substance can never become altogether non-conducting ; the 



A'OL. LXVI. 2 O 



