460 Prof. J. C. Bose. On Mectric Toicch and the Molecular 



(a) Of the allotropic transformation being attended with changes 



in the conductivity of the substance. 



(b) Of the existence (and, if possible, the production by chemical 



means) of an allotropic modification analogous to the radia- 

 tion product or B variety, whose reaction should be opposite 

 to that of the substance in a normal condition (A variety). 



(c) Of the assumption that after the maximum transformation of 



A into B, the further action of radiation is to reconvert, to a 

 more or less extent, the form B into A, such transformations 

 gi^dng rise to electric reversals. 



(d) Of the existence of the radiation product in a fatigued 



specimen. 



The above mentioned hypotheses will obtain still stronger support if 

 further deductions from the above theory are borne out by confirmatory 

 experiments. 



I will now describe investigations on the lines sketched above. 



Allotro]}ic Modification produced hi Visible lladiation. 



As regards the action of radiation in producing allotropic modifica- 

 tion, several such instances are known in the case of visible radiation. 

 In the familiar example of the conversion of yellow phosphorus into 

 the red amorphous variety, the effect is quite apparent. But this is not 

 the case in the transformation of the soluble sulphur into an insoluble 

 variety by the action of light ; here the transformation is not apparent, 

 -and has to be indirectly inferred from the insolubility of the solarised 

 product in carbon bisulphide. The reason why a far larger number of 

 instances of allotropic transformation produced by light is not known 

 is not because such effects are not more numerous, but because we 

 are unable to detect such changes. It must be admitted that our 

 knowledge of molecular changes, specially in a solid, and the means of 

 their detection, is at present extremely limited. 



Varicdioii of Coiicliictivity irroclaced by Allot rojnc Changes. 



There is one method of detecting these molecular variations to which 

 little attention has hitherto been given, but which appears to be of 

 great interest, and promises to yield important results in investigations 

 of this class. It is evident that changes in molecular structure must be 

 attended with changes of physical properties, electric conductivity 

 being one of them. Among other instances of allotropic changes 

 attended with changes in electric conductivity may be mentioned the 

 wide difference of conducting power between graphite and diamond. 

 The same great differences of conductivity is seen between the crystal- 

 line and amorphous ^ arieties of silicon, and between the " metallic " 



