DR. LODGE'S remarks on p. 513 (April 2), ought not, I think, to pass without protest. He very reasonably objects to being asked to use a formula which is adapted to one particular set of units, and is ...

PROF. GREENHILL, on p. 462 (March 19), gives a naïve and most instructive description of the straits to which a “practical man” is put when he wishes to interpret the simplest general formula.