Societies and Academies

Abstract

MANCHESTER. Literary and Philosophical Society, December 1.—Mr. F. Nicholson, president, in the chair.—C. H. Lander: Graphical determination of the stresses in the main spars. of monoplanes. One of the most complex problems connected with the design of beams con- tinuous over several supports is presented by the main spars of monoplanes. The stresses are made up of direct compressions and those due to bending moments, the determinations of the latter being most complicated. The lift of a wing surface for small angles increases with the angle of incidence and with the square of the velocity: at a speed of about 6o miles per hour the lift of a certain type of curved wing varies from 5 lb. at 4° up to a maximum of 11.7 lb. at 17° at 120 miles per hour these lifts would be four times as great. Most monoplanes are designed for a load of 0.007V²lb. per square foot, V teing the designed speed in feet per second. From this the loading on the spar may be determined for different angles. The method of solution of the stresses then varies according to the manner in which the lift wires are attached to the spar. The direct application of Claxton Fidler's method of solution of continuous beams may be used when the lift wires are attached to the spar at the neutral axis. When these wires are attached at the lower side of the spar, the longitudinal moments induced may be assumed and their diagrams plotted as though the spars were discontinuous over the points of support, characteristic points obtained, and the true base line drawn by Fidler's method. A modification of Fidler's method can also be used in the case of wires badly adjusted or injured.—Prof. W. H. Lang: Studies in the morphology of Isoëtes. Pt. I.—The general morphology of the stock of Isoëtes. The external form and gross anatomy of the two-lobed stock of Isoëtes lacustris is described. The upper portion of the stock corresponds to the shoot, the lower portion behaves as a downwardly growing rhizophore, on which roots arise in acropetal succession. The position of the deeply-seated growing line of the rhizophoric region corresponds to that of the secondary meristem of the base of the stem, but its mode of growth is different. The growth proceeds, and the roots are brought to the surface, as if the lower apexwere not only drawn out and deeply sunken, but the opposed sides of the depression were congenitally united. When the roots are exposed by the splitting proess at the groove they stand exogenously on the surface. This mode of Interpreting the morphology of Isoëtes proves satisfactory when applied either to the explanation of the growth of the stock itself or in comparisons with Lepidodendrere and Pleuromeia. The rhizophoric region of the stock of Isoëtes is regarded as the structure in existing plants most closely comparable lo the stigmarian base of the Lepidodendrereæ.