"The photographic record is ready for the computer in from six to ten seconds, and the gun position can be found and plotted in three or four minutes. "Sound ranging also can be used for ranging our own guns with great accuracy. When a record has been obtained of a hostile gun, all that need be done is to record the burst of our own shell and give corrections to our battery until the record of our shell-burst is identical with that of the hostile gun. The shell must then be on the target. "The system works equally well by day or by night, in rain or in fog. Its one enemy is a wind which blows towards the hostile gun and prevents the sound reaching the recording apparatus. It can detect a gun as easily if it is in a wood or in a building as if it were on a hill-top. "Simple as it appears, however, it is not so easy as one might think to make a practical ally of sound ranging. We have succeeded. The Germans failed. Towards the end of the war at least ninety per cent, of the German artillery was marked down accurately by these means; and the staff employed on sound-ranging and flash-spotting (the last a kindred method depending on a mixture of observation and mathematics) had grown from _four_ in 1914 _to four thousand five hundred_ in 1918. "Casualties have been heavy, and the work arduous. But those responsible for it have, at any rate, 'done their bit.'" This is just one instance, such as we ignorant at home can more or less follow, of that concentration of British wit and British perseverance on the terrible business of war which carried us to our goal. Germany prided herself, above all, on "scientific war." But the nation she despised as slow-witted and effete has met her again and again on her own boasted ground, and, brain for brain, has won. With the ever-growing importance of artillery has gone, of course, a constant increase in artillery _personnel_, and in the proportion of gunners to infantry. The Third Battle of Ypres in the autumn of 1917 was "one of intense struggle for artillery supremacy," says the Field Marshal. Germany had put out all her strength in guns, and was determined to beat down the British artillery. The British Command met the attack and defeated it, in a long-drawn battle, in which, naturally, the proportion of artillery _personnel_ to infantry was exceptionally high--at one time eighty-five per cent. Last spring, for a short time, owing to the transference of batteries from the Russian front, the enemy command succeeded in establishing "a definite local artillery superiority." But it was soon over. Before the breakdown of the March offensive "our guns had regained the upper hand," and in the later battles of the year the German artillery was finally mastered.