of the Approach and Recession of Bodies. 81 



pounds, and may have other powers of a mechanical, 

 chemico-mechanical, or other hitherto undiscovered nature. 



" The very doctrine of the equivalency and convertibility 

 of the natural forces implies, that we may have any kind 

 of energy as the educt of any other kind. These same rays 

 of high refrangibility are those which are absorbed by the 

 leaves of the plant, and constitute the force by which the 

 timber is grown, thereby effecting an enormous store of 

 mechanical energy. 



\ ' Dr. Guthrie's experiments would appear to prove that, 

 with aD intervening vibrating ponderable medium, approach 

 between bodies freely suspended is a natural consequence. 

 But whether this applies, in an equal sense, in the case of a 

 vibrating imponderable aether is not so apparent. 



" We know that the latter are potent in effecting molecular 

 motions, and we know that molecular motions anticipate the 

 motions of the mass, as instanced by nitro-giycerine. 



" But, with reference especially to these recessions of the 

 balance, what we want to know at present is, — What would 

 be the behaviour of a body, freely suspended, and proved to 

 be wholly freed from all vaporizable constituents, in a 

 perfect void, under the influence of the several varieties of 

 radiant energy % " 



In closing, the author begged to record his best thanks to 

 Mr. George Foorcl, of the Melbourne Mint, for having most 

 kindly placed his private laboratory at the author's disposal, 

 whilst conducting these experiments, for the pains he took 

 to construct with his well-known skill the most delicate of 

 the apparatus employed, and for his advice and sympathy 

 throughout the enquiry. 



DESCRIPTION OF PLATE. 



a Bulb to be exhausted of air, containing balance — the subject of 



experiment. 

 & Tube from Sprengel branching into c and d. 

 c Branch tube leading to bulb. 



d Branch tube dipping into mercury in trough e and constituting gauge. 

 / Barometer standing side by side with gauge. 



The scales of barometer and gauge are en tubes external to each, 

 adjusted by the keys g and cords passing over pulleys at h. 



A. B. C. D. Enlarged drawings of details. 



Note. — For clearness, certain minor details of construction are omitted 

 in the drawing. 



G 



