Mr. H. F. Baxter on Nerve Force, 11 



the only form in which absorption shows itself; it can, as is well 

 known, appear as chemical agency, fluorescence. 



The chemical action must, however, be under the same rule as 

 the thermometric heat, viz. that a ray will show a more powerful 

 chemical agency in proportion to the ease with which the smallest 

 constituent parts of which a molecule may be considered as com- 

 posed assume certain oscillatory motions. 



Fluorescence and phosphorescence, on the other hand, cannot 

 be explained on the grounds set forth in the foregoing articles. 

 In the first place, it must be considered as a law of nature that, 

 as long as light and radiant heat preserve their form of undulatory 

 motion, the period of oscillation remains unaltered. This, as 

 appears from the experiments of Melloni and Knoblauch, is also 

 the case with diffused heat, which moreover ceases instantaneously 

 with the radiation that produces it. Fluorescence, on the con- 

 trary, is similar to thermometric heat, in the circumstance that it 

 is independent of the source of heat, and moreover, according to 

 the researches of Becquerel, does not cease instantaneously on 

 the cessation of the radiation. But, in the next place, since the 

 composition of thermometric heat depends only on the nature of 

 the body itself, and since a certain high temperature, and there- 

 with determinate amplitudes in the vibrations of the body's 

 minutest parts, are always necessary in order that these latter 

 may appear in a state of incandescence, it follows that fluorescent 

 light cannot belong to the body's own molecules. Add to this, 

 that fluorescence is ordinarily of very short duration and gives a 

 discontinuous spectrum, whereas the spectrum from an incan- 

 descent solid body is continuous. 



The only method, then, that I see of explaining fluorescence is 

 to consider it as generally consisting in pendulous motions of the 

 aether, analogous to those of thermometric heat, or else in per- 

 manent undulations. This supposition offers a complete analogy 

 between the phenomena of sound and light ; for as the air can 

 at once propagate sound and be itself the resonant body, so can 

 aether at once propagate the light-wave and be itself the cause of it. 



II. On Nerve Force. — Relation of Nerve Force to Electric Force. 

 Origin of Nerve Force. By H. F. Baxter, Esq.* 



HAVING partly considered the present question on a former 

 occasion, I will briefly recapitulate the conclusions that 

 were then arrived at, referring my readers to the published 

 papers f for the arguments upon which they were established. 



* Communicated by the Author. 



t Organic Polarity. Churchill, London, 1860, Edinburgh New Philo- 

 sophical Journal, July 1860. 



