SCIENTIFIC DISCOVERY

Waipa Post, Volume 37, Issue 2227, 27 October 1928, Page 3

SCIENTIFIC DISCOVERY

HOW THE BRITISH GUNS WERE \ RANGED. “It was in the early days of the war,” said Sir William Bragg, in a presidential address to the annual meeting of the British Association for the Advancement of Science, that a body of young scientific students from our universities was assembled for the purpose of testing on the battlefield the value of such methods of locating enemy guns as were already known. “In their mutual discussions and considerations it became clear to them that the great desideration was a method of measuring exactly the time of arrival of the air pulse, due to the discharge of the gun, at various stations in their own lines. “If. the relative positions of the stations', were accurately known it would then become a matter of calculation to find gun position. But the pulse was very feeble: how could itl be registered? FINE WIRE METHOD. “Various methods were considered, and among them was one which no doubt seemed far-fetched and unlikely to be successful. “A fine wire is made to carry an electric current by which it is heated. If it is chilled, for example, by a puff of cold air, the resistance tb the passage of the current increases, and this is an effect which can be measured if it is large enough. <«, “If then,, the hot wire coulkl be made to register the arrival of the air pulse from the gun a. solution of the problem was in hand. “But, and this was the most important point, was it! to be expected that the effect, though it must be there, would be big enough to see? Could the faintl impulse from a gun miles away produce an obvious chill in a hot wire? On first thoughts it did not seem likely, and the suggestion lay in abeyance. SHELLS AT DAWN. “But it happened that one summer morning an enemy aeroplane came over at' daybreak on a patrolling expedition. The officer of whom I have spoken lay awake in his bunk listening to the discharges of the antiaircraft guns and the more distant explosions of their shells. “Every now and then a faint whistling sound seemed to be connected with the louder sounds. The wall of the hut was of felt; it was in poor condition, and there were tiny rents close to his head as he lay. The gun pulses made, a feeble sound as they came through. “This set the officer thinking: if the pulse was strong enough to make a sound, it might! be strong enough to chill a hot wire perceptibly. “So the method was proposed to the company as worth trying. It was tried and proved tlo be a complete success. The sound ranging of the British armies was based upon it, with results which have already been described and are fairly well known.”