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European Agent: William Wesley & Son, 28 Essex St., Strand, London, and Mayer and Müller, Prinz Louis-Ferdinand Str., Berlin. Exchanges.-The JOURNAL does not exchange with other publications. Missing Numbers will be replaced without charge, provided that claim is made within thirty days after date of the following issue. • Volume I, however, from July 19, 1911, to December 19, 1911, will be sent for $3.00. Special rates are given to members of scientific societies affiliated with the Academy. THE WAVERLY PRESS BALTIMORE, U. S. A. 1 ARTILLERY.-The problem of anti-aircraft firing. X. REILLE. Lieutenant Colonel, Chief of Artillery in the French Advisory Mission. (Communicated by L. J. Briggs.) At the beginning of the war it was almost impossible to foresee what would be the development of aviation in the army and what developments in anti-aircraft artillery would of necessity follow. The object of artillery against aircraft is above everything else to prevent the enemy machines from fulfilling their mission of observation. Although there are those who seem to think that the present and future rôle of aviation consists mainly in dropping bombs, it must be said that this is a decided error. The principal rôle of aviation is not in the dropping of bombs but in observation. The flying machine should be considered not so much one of the arms of the artillery as one of its eyes-and that eye the better one. In fighting the enemy aircraft our guns fight the artillery of the enemy in its most vital part. The artilleryman who fires, or orders firing, against aircraft should never forget the importance of his rôle, which is to render the artillery of the enemy practically useless by blinding it. At the outbreak of the war there were only a few types of anti-aircraft guns in our army, and as far as we know there was no special anti-aircraft gun in the German army. On both 'A lecture given before the Washington Academy of Sciences on April 18, 1918. sides, the aircraft war was considered as a supplementary duty for the field matériel and this duty had to be fulfilled by whatever means could be improvised (burying the trail of the gun, etc.). In proportion as the war developed, the invention and extension of a special anti-aircraft matériel have taken on greater and greater importance in the armies of the Allies as well as in the German army, and this in proportion to the importance taken by the means employed for aerial observation. The object of this lecture is not to study the improvements made in anti-aircraft matériel but to follow in its different stages and up to the point where it is, today, the study of the general problems which anti-aircraft war has presented to the minds of artillerymen. I As long as the objectives of artillery were terrestrial targets the interest in the study of the trajectory seemed to be limited: (a) To the initial part of the ascending branch (angle of elevation, angle of jump, angle of projection or departure, clearing angle, etc., etc.). The study of the initial part of the ascending branch was entirely oriented in the double problem of defilade and range. (b) To the terminal part of the descending branch (angle of fall, angle of impact, angle of protection, angle of ricochet; the apparent elevation of the burst, etc.). The study of the terminal part of the descending branch was entirely oriented in the problem of the vulnerability of the target according to its nature or its location. When it was a question of firing at aerial targets the tendency at first was, and this is easily comprehensible, to argue in regard to these targets as if they were merely terrestrial targets raised to a very high angle of sight. One of the first results of this theory was to erroneously apply to these targets: first, the idea of a normal height of burst (hauteur type) above the target that would give the maximum effect; second, the hypothesis of the rigidity of the trajectory. |