A further note upon "inter-traction."

I pointed out in a previous communication that a mixture of fluids can be brought about not only by the operations of mechanical convection and diffusion, but also by the impulsion of a force which can very rapidly carry down a lighter overlying fluid into a heavier underlying fluid in the form of characteristic pseudopodial streamers, conveying at the same time the heavier underlying fluid into the lighter superjacent fluid in the form of a palisade of ascending streams. I have ventured to call the agency by which this reciprocal instreaming is produced:― inter-traction . These phenomena which I described as occuring when salt, and also sugar, solutions brought into contract with albuminous solutionscan, as Schoneboom showed, be obtained also with a very wide range of substances; and they have been ascribed by him to the operations of negative interfacial tension, and identified with phenomena theoretically anticipated by Clerk-Maxwell. Adam and Jessop, in a further communication, have insisted that the pseudopodial streaming is attributable to operations of diffusion and resulting changes in specific gravity, and they have stressed the point that the characteristic appearances can be obtained only when the lighter is superposed upon the heavier fluid, and not when the fluids are disposed side by side. In view of the fact that the conclusion that horizontal streaming cannot be obtained rests only upon experiments conducted by filling fluids of different specific gravity into adjoining cell compartments, and then removing the dividing wall, it seemed desirable to try for horizantal inter-traction with a technique which would get rid of the complication of the heavier fluid sinking to the bottom and the lighter going to the top of the vessel, and would allow of more accurate and deliberate observation. The quite simple technique now to be described satisfies these desiderata.