to determine his height, his speed or the direction in which he is moving, to enable him to drop his bomb at the right moment, or to sight his gun on his enemy as the two planes come within range. Cambridge, as represented by Horace Darwin and Keith Lucas, has done yeoman service in these various fields, while in all our many discussions on theory we have profited by the great knowledge and the clear thinking of our Chancellor Lord Rayleigh, President of the Advisory Committee for Aeronautics.
Again, turning to another subject, consider the science involved in the manufacture of a big gun and its ammunition, or in the calculation of the trajectory of its projectile. Many gun problems are not new: artillerists have long realised the importance of experiment and calculation, the manufacturer to test his steel and determine the safe stresses to which
