Bache.] J- '4: [April 20, 



these is as free as in aqueous solutions; and I think more so. So 

 molecular movements of solid particles in suspension in aqueous 

 fluids must take place perforce of the constant repulsions of the con- 

 stituent molecules of the particular liquid present — water. The 

 minute drops of oils supernatant on water, some of them no larger 

 than the particles in the water below, observed by Dr. Brown, as he 

 says, to be almost or wholly motionless, so behave because the 

 molecules of water glide by the molecules of a substance for which 

 they have not even the affinity that would compass opposition. Be 

 the globules of oil on water never so small or large, the molecules of 

 the aqueous fluid glide by them. Whether a small or a large 

 globule of oil be the particle itself on water, there is no movement 

 of the particle. Dr. Brown says none, or almost none. I think 

 that he was mistaken, that there is no molecular movement whatever. 

 Fixed oils have not the same molecular constitution as volatile 

 oils, nor these the same as alcohol, nor either the same as water. 

 Whatever these differences may signify in various behaviors, under 

 varying conditions, one, among the rest, distinguishes water from the 

 rest and all other liquids. Despite its apparent perfect fluidity, the 

 reluctance of its molecules to move among themselves as smoothly 

 as do those of other liquids among themselves is one of its most 

 evident characteristics. We see this exemplified by the way, long 

 since ably demonstrated, in which a wave is built up from ripples, 

 by the way in which the surf breaks along the shore, and in the 

 ease with which a small proportion of oil in contact with water 

 modifies or subdues its energy. Only recently I steered a boat in 

 Boston harbor between two headlands, between which, and far 

 beyond, white-caps covered the surface of the water, surrounding a 

 placid lakelet of a square mile in area, black by contrast to its 

 white-capped margin, over the surface of which lakelet I was soon 

 smoothly gliding; and this change from turbulent to placid waters 

 was wholly due to the merest film of oil from Boston's great sewer 

 discharging its contents three miles away on the lowering tide from 

 the head-house on Moon Island into the current running towards 

 the sea. I am aware, of course, that part of the calmness described 

 was owing to the fact that the oil lessened the friction of the wind 

 on the water. But that was not the only cause of the calming 

 effect i)roduced by the oil. Oil prevents the friction of parts on 

 the surface of water already in agitation, and thereby quiets the 

 wave already risen. The area which I have just described as a 



