in reply to his Animadversions. 419 



M. Moser's, or otherwise. I have seen paragraphs stating 

 that M. Moser has succeeded in copying engravings from 

 paper, but I do not, even now, know his experiments. I shall 

 not dispute with M. Moser the point of priority, but I trust he 

 will do me the justice of acknowledging, that he has judged 

 hastily in accusing me of having appropriated his experiments 

 without acknowledgement. In the paper in question I thought 

 I had sufficiently acknowledged the high merits of Professor 

 Moser ; I again do so. He has opened a new and important 

 path of physical inquiry, which promises to lead to some great 

 truths connected with the constitution of matter, and the ope- 

 rations of the imponderable elements ; at the same time, how- 

 ever, that I admit the importance of his discoveries, I must be 

 allowed, for the present, to dissent from his conclusions. 



It is not my intention to offer any further remarks in expla- 

 nation of that portion of M. Moser's paper which particularly 

 applies to myself, but I must be allowed this opportunity of 

 reviewing some of the opinions he has put forth, and of ex- 

 plaining my reasons for differing from him. 



M. Moser states that every body must be considered as self- 

 luminous, and he appears to view the accelerating power ex- 

 erted by heat, as stated in his own experiments, as the influ- 

 ence of caloric increasing the intensity of the invisible radia- 

 tions, whilst as " their temperature becomes higher their re- 

 frangibility decreases." It becomes necessary, in the first place, 

 to ascertain upon what evidence this self-luminosity of bodies 

 is asserted. It has been long known, that light acting upon 

 ioduret of silver, alters its condition, and renders it capable of 

 condensing the vapours of mercury in a remarkable manner; — 

 this constitutes the Daguerreotype. It has been shown that 

 if we breathe over portions of a metallic plate, the other parts 

 being covered, and then the vapour is allowed to dry off, the 

 plate is in a condition to receive vapours over definite spaces, 

 in the same manner as if it had been exposed to the light. 

 Again, any solid body being placed for a short time on a po- 

 lished plate of metal or of glass, either of them become sus- 

 ceptible of receiving vapory deposits, which will mark di- 

 stinctly the spaces occupied by the bodies in contact. " By 

 these experiments, I think," says Moser, ** I have proved that 

 contact, cotidensation qf vapours, and light produce the same effect 

 on all bodies'" and hence he rushes to the conclusion that all 

 bodies are self-luminous, and has even speculated on the co- 

 lour of the latent light of vapours, in a way, which betrays his 

 fears lest the hypothesis he has framed should be destroyed 

 by his own results. Light, or rather, as I am inclined to 

 think, some element intimately connected with light, and 



2E2 



