Bache.] 3- * P [April 20, 



claim to have detected is a phenomenon which reverts to the 

 molecular constitution of water, as to which the moving, solid par- 

 ticles in it concerned in the brownian movement have no more to 

 do than has a current-metre to do with the flow of the stream the 

 swiftness of which it measures. We do not deny that a gas may be 

 essentially pure, and therefore homogeneous, a chemical as well as 

 physical entity, and that, nevertheless, its molecules may have 

 repulsions among themselves : on the contrary, we affirm it. Simi- 

 larly water, recognized, as it is, as a chemical condition, not a me- 

 chanical mixture, has, as here demonstrated, repulsions among its 

 molecules. 



When I take into account all that I have detailed, and remember 

 also that these moving particles of which we have been speaking, 

 .hermetically sealed under glass, as I have them now under cover- 

 . glasses, move indefinitely in time, unmodified in range and veloc- 

 ity, through changes of temperature, through light and darkness, 

 through electricity and magnetism, in the presence of every force 

 to which I have been able to subject them, I cannot but think, 

 when I add that these movements are active in proportion to the 

 fineness of subdivision of the particles, that they are caused by the 

 mutual repulsions of the molecules of aqueous fluids. Did I see a 

 relatively large mass moving as vigorously as the most minute one 

 visible to the eye, I should regard this theory as untenable from 

 that single fact alone, because it would be impossible that molecu- 

 lar action should concentrate effect on a relatively great mass; but 

 when I see, as I do, the largest masses remaining unmoved, and 

 .descending in the scale, smaller ones, showing the effects of a faint 

 ■impulse, and descending further still, others exhibiting sluggish 

 ■ movement, until the sight reaches the smallest particle visible, 

 finding in that the most eccentric and vehement movement of any 

 exhibited, I know then that I am looking at a sea where the little 

 waves dash in vain on the impressionless rocks, barely disturb the 

 floating ships and hulks, but twist and swirl and make frantically 

 dance the little cockle-shells of boats wherever they may happen to 

 be upon the surface; and that, in fine, I am witnessing the molec- 

 ular movement of this sea in its effort to escape into space. The 

 aqueous fluids, finding no release, as under my cover- glasses, the 

 movements would go on forever; finding it in freedom from con- 

 finement, they go on until the fluid which is the condition of their 

 manifestation is in a. few minutes dissipated in evaporation. 



