THE PHILOSOPHY OF THE RADIOMETER. 



THE PHILOSOPHY OF THE RADIOMETER AND 

 ITS COSMICAL REVELATIONS. 



So much speculation, and not a little extravagant specu- 

 lation, has been devoted to the dynamics of the radiometer, 

 that I feel some compunction in adding another stone to 

 the heap, my only apology and justification for so doing 

 being that I propose to regard the subject from a very un- 

 sophisticated point of view, and with somewhat heretical 

 directness of vision i.e., quite irrespective of atoms, mole- 

 cules, or ether, or any other specific preconceptions con- 

 cerning the essential kinetics of radiant forces, beyond that 

 of regarding such forces as affections or conditions of mat- 

 ter which are transmitted radially in constant quantity, and 

 therefore obey the necessary law of radial diffusion or in- 

 verse squares. 



The primary difficulty which appears to have generally 

 been suggested by the movements of the radiometer, is the 

 case which it seems to present of mechanical action with- 

 out any visible basis of corresponding reaction : a visible 

 tangible object pushed forward, without any visible push- 

 ing agent or resisting fulcrum against which the moving 

 body reacts. 



This difficulty has been met by the invocation of obedi- 

 ent and vivacious molecules of residual atmospheric matter, 

 which have been called upon to bound and rebound between 

 the vanes and the inner surfaces of the glass envelope of 

 the instrument. 



How is it that the advocates of these activities have not 

 sought to verify their speculations by modifying the shape 

 and dimensions of the exhausted glass bulb or receiver ? * 

 If the motion of the radiometer is due to such excursions 

 and collisions, the length of excursion and the angles of 

 collision must modify its motions ; and such modification 

 under given conditions would form a fine subject for the 

 exercise of the ingenuity of molecular mathematicians. If 



* Since this was written some such modifications have been made 

 with equivocal results. 



