246 SCIENCE AND METHOD. 



judicious use of the theorem of virial will enable us 

 to realize this. 



We may transform Lesage's theory by suppressing 

 the corpuscles and imagining the ether traversed in 

 all directions by luminous waves coming from all 

 points of space. When a material object receives a 

 luminous wave, this wave exercises upon it a mechani- 

 cal action due to the Maxwell-Bartholi pressure, just as 

 if it had received a blow from a material projectile. 

 The waves in question may accordingly play the part 

 of Lesage's corpuscles. This is admitted, for instance, 

 by M. Tommasina. 



This does not get over the difficulties. The velocity 

 of transmission cannot be greater than that of light, 

 and we are thus brought to an inadmissible figure for 

 the resistance of the medium. Moreover, if the light 

 is wholly reflected, the effect is nil, just as in the 

 hypothesis of the perfectly elastic corpuscles. In 

 order to create attraction, the light must be partially 

 absorbed, but in that case heat will be produced. The 

 calculations do not differ essentially from those made 

 in regard to Lesage's ordinary theory, and the result 

 retains the same fantastic character. 



On the other hand, attraction is not absorbed, or 

 but very slightly absorbed, by the bodies it traverses, 

 while this is not true of the light we know. Light 

 that would produce Newtonian attraction would re- 

 quire to be very different from ordinary light, and 

 to be, for instance, of very short wave length. This 

 makes no allowance for the fact that, if our eyes were 

 sensible to this light, the whole sky would appear 

 much brighter than the Sun, so that the Sun would 

 be seen to stand out in black, as otherwise it would 



