LONDON. Royal Society, June 24.—Prof. J. Cossar Ewart, vice-president, in the chair.—Pressure perpendicular to the shear, planes in finite pure shears, and on the lengthening of loaded wires when twisted: J. H. Poynting. When a solid is subjected to a finite pure shear the lines of greatest elongation and contraction are not the diagonals of the rhombus into which a square is sheared, but lines making, respectively, ±ɛ/4 with the diagonals of the square, xvhere e is the angle of shear, and these lines are at right angles to the order of ɛ2. If we assume that a pressure P is put on along the lines of greatest contraction, and a tension Q along the lines of greatest elongation, we may put P = uɛ + pɛ2, Q = uɛ - pɛ2, where u is the rigidity and p is a constant to the second order of e.