304 Actinism and Magnetism. [July, 



silver and the ultimate of iodine, rather than such as might 

 be expected in the movements of the entire molecules of 

 iodide of silver. 



It will be perceived that it is only the latent image in the 

 case of the iodised films, either in the Daguerreotype or 

 collodion processes, that requires for its explanation the 

 help of the assumption, that the ether consists of two 

 perfectly elastic fluids intimately mingled together, yet 

 capable of partial temporary separation. Should this same 

 assumption be eventually found available for explaining 

 the duality observed in the phenomena of electricity, para- 

 magnetism and diamagnetism, the evidence in favour of the 

 hypothesis will be greatly strengthened by the circum- 

 stance of its being thus found to render such aid in 

 explaining a phenomenon so diverse from these as the 

 latent image. 



The facts that metallic zinc, when thrown into a state of 

 heated vapour, generates in the ether waves which, though 

 wholly invisible, yet exert much actinism, and that alu- 

 minium, under similar circumstances, originates invisible 

 waves capable of exciting fluorescence, favour the idea that 

 the influence of the solar radiation on the magnetic needle 

 may also be due to waves which are in like manner in- 

 visible. Experiments have been several times made with 

 the wiew of showing that the violet and ultra violet waves 

 do affect the magnetic needle ; but the results, probably 

 owing to the difficulties attending the experiment, have 

 not been decisive. It would not be easy, however, to 

 account for the known effect of solar radiation on magnets 

 — more especially the effect of solar spots — otherwise than by 

 supposing that there are special waves of some sort that 

 pass through the ether, and either excite or alter the mag- 

 netic condition. If such be the case, then will it be pro- 

 bable that, exactly as all bodies which receive an accession 

 of temperature from the solar energy give it off again by 

 radiation, even so all magnetic bodies receiving an acces- 

 sion of magnetism from the solar energies give it off again 

 in a similar manner, propagating from themselves back 

 waves having a great rapidity of vibration — too great to 

 be appreciable by the optic nerve, but nevertheless capable 

 of exciting or maintaining either paramagnetism or dia- 

 magnetism in other bodies. Nor does it seem to be im- 

 probable that, as in the case of fluorescence, in which there 

 is a change in the rate of vibration operated by the action 

 of the ponderable particles, there may be, in the case of the 

 magnet, something similar. Magnetic bodies may have 



