324- Sir Humphry Davy on the Colour of Water, 



results from the reciprocal influence of active fluids upon ac- 

 tive solids, and of active solids upon active fluids. It is suffi- 

 cient that one only of these elements of action be inactive, that 

 the endosmose may not take place. 



Thus, for example, every thing being arranged convenient- 

 ly for endosmose, this action will be suspended by the ad- 

 dition of a little sulphuric acid to the fluids, because this acid 

 is an inactive fluid. It will be also in vain that the two hete- 

 rogeneous fluids be active. If the permeable membrane which 

 separates them is inactive, there will be no endosmose. 



Thus it is demonstrated that this phenomenon results from 

 two combined actions ; 1st, the action of the fluid upon the 

 solid ; 2d, the action of the solid upon the fluid. These two 

 actions, which are indubitably electrical actions, have evidently 

 their seat in the thickness or in the substance itself of the per- 

 meable membrane which constitutes the active solid. It is a 

 capillo-electrical phenomenon, or one of intra-capillary electri- 

 city. From this we may understand why this electricity 'does 

 not appear in the galvanometer. It is not all exterior, it is in 

 the capillary pores that the dev elopement of this impulsive electri- 

 city is produced ; and this state of electricity is given to the 

 capillary pores in two manners ; 1st, by the action of the two 

 opposite poles of the pile upon the two opposite faces of the 

 active permeable membrane ; 2d, by the contact of two hetero- 

 geneous active fluids upon the two opposite faces of the mem- 

 brane. Thus it is the influence of the contact of the fluids 

 upon the solid which communicates to this last the state of ca- 

 pillo-electricity, and it is the influence of the capillo-electrified 

 solid upon the fluids which communicates impulsion to them. 



Art. XXIII. — Observations on the Colour of Water, and on 

 the Tints of the Ocean. By Sir Humphry .Davy, Bart.* 



The purest water with which we are acquainted is undoubted- 

 ly that which falls from the atmosphere. Having touched air 

 alone, it can contain nothing but what it gains from the atmos- 



* From Sir Humphry's admirable volume entitled Salmonia, or Days of 

 Fly-fishing, London, 1828, a work replete with scientific observation, 

 good feeling, and unaffected piety. 



