PHYSICAL RESEARCHES CONTINUED 77 



the new variety to the familiar one ; and on stimulation 

 he also found repeated reversals from + to , and back 

 again, thus giving an alternating curve. The change 

 induced in various substances by electric radiation seemed 

 to Bose plainly one of molecular strain in response to 

 external stress. So, he asked himself, do not such varia- 

 tions, sufficiently marked and permanent, give the physicist 

 a peep into the chemist's (hitherto empirical) collection of 

 ' allotropic substances/ and even a method towards their 

 further investigation ? For if the transient allotropism 

 thus discovered be thought of as molecular strain, with 

 the possibility of recovery, then ordinary allotropism, so 

 relatively stable, becomes also comprehensible i.e. in 

 terms of over-strain, from which spontaneous return is 

 difficult or impossible under ordinary conditions. 



This delicate mode of inquiry was rightly claimed 

 as ' full of promise in many lines of inquiry in molecular 

 physics. . . . The varieties of phenomena are unlimited ; 

 for we have in each substance to take account of the pecu- 

 liarity of its chemical constitution, the nature of its response 

 to ether waves, the lag and molecular viscosity. All these 

 combined give to each substance its peculiar characteristic 

 curve : it is not unlikely that the curves may give us 

 much information as to the chemical nature and physical 

 condition of the different substances.' Bose's new investi- 

 gations had been to disclose a new class of phenomenon 

 of which electro-optics had given no suggestion, those of the 

 different touch of metals, when employed as materials of 

 so many ' Coherers/ or rather receivers. Here, returning 

 to the chemical suggestions above noted, was an interesting 

 correlation of electric properties with atomic weights, and 

 the disclosure of a new arrangement of these accordingly 

 one not without suggestive analogies to MendeleefFs famous 

 classification, and inviting therefore fresh research. 



Return now to the nature of the electric radiation 

 discussed in Chapter IV : first, as an extended spectrum 

 of longer and longer waves beyond those of heat, and yet, 





