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VII. Note on the Experiments of Moser. {Extract from the 

 Giornale Toscano di Scienze Mediche, Fisiche, $r.)* 



THE experimentsf of Moser, of which we have cited an 

 extract made by Mr. Plantamour {Bill. Univ., April 

 1843, p. 370), are such as to excite the curiosity and interest 

 of the learned, by their singularity and by the kind of mystery 

 in which their explanation is still involved. We think, never- 

 theless, that before we have recourse to new and occult forces 

 or to new properties of forces generally admitted, it is right to 

 endeavour to account for them by explaining them by means 

 of forces, the laws and nature of which we are already ac- 

 quainted with. The experiments appear to us somewhat con- 

 nected with those which Prevost, Carradori and Lehot made 

 several years ago on the adhesion between liquid drops and 

 the polished surfaces of solids, a subject which has lately en- 

 gaged the attention of Dutrochet. The ignorance in which 

 we still remain of the laws which govern these phaenomena 

 can alone lead us to comprehend how so skilful an observer 

 as M. Dutrochet can have been induced to imagine a new 

 force which he calls epipolic, or the force of superficies. The 

 following is one of the principal conclusions to which Moser 

 has been led by his experiments : — 



" The condensation of vapours on the plates produces a 

 modification upon their superficies, which is indicated by a 

 difference in the successive condensation of the vapours which 

 adhere to them, or which alter them chemically." 



The simplest of the experiments which lead to this result 

 may be made by breathing upon one of Daguerre's plates, or 

 on a plate of steel or glass, or on the surface of a layer of mer- 

 cury after having covered this surface with a diaphragm having 

 apertures in it. In this way the vapour condenses on some 

 points and not on others; these latter evidently are the por- 

 tions of the surface covered by the diaphragm. When this is 

 taken away all disappears after a few seconds; but it is only 

 requisite to breathe again in order to witness the reappearance 

 of a figure which represents the diaphragm with all its open 

 spaces. If the manner in which the condensed vapour disap- 

 pears from the different points of the surface be attended to, 

 we shall see that the parts of the diaphragm which are not co- 

 vered, and where the vapour had been condensed at first, are 

 those from which it soonest disappears. 



On examining the plate which was breathed on a second 



* From the Bibliothvque Universelle for August 1843; vol. xlvi. p. 374. 

 •f- For Moser's account of these experiments see Taylor's Scientific Me- 

 moirs, vol. iii. p. 422, et seq. 



