On the analogy between this case and that of the **interface** between two solutions, Nernst has arrived at similar logarithmic expressions for the difference of potential, which becomes proportional to log (P 1 /P 2) where P2 is taken to mean the osmotic pressure of the cations in the solution, and P i the osmotic pressure of the cations in the substance of the metal itself.

[In order to express the dependence of the tension at the **interface** of two bodies in terms of the forces exercised by the bodies upon themselves and upon one another, we cannot do better than follow the method of Dupre.

If T12 denote the interfacial tension, the energy corresponding to unit of area of the **interface** b Q FIG.

On the whole, then, the work expended in producing two units of **interface** is 2T1+2T2-4T'12, and this, as we have seen, may be equated to 2T 12.

If 2T'12>T1+T2, T12 would be negative, so that the **interface** would of itself tend to increase.

For instance, if T31> T12+ T23, the second fluid spreads itself indefinitely upon the **interface** of the first and third fluids.

We are thus led to the important conclusion that according to this hypothesis Neumann's triangle is necessarily imaginary, that one of three fluids will always spread upon the **interface** of the other two.

If I am trying to portion my meals better, I could ask it, through a verbal **interface**, to vibrate gently when I reach seven hundred calories in that meal.