The officer in charge of the battery, knowing the height of the airship, is able, by means of the angle thus given him, to get the distance between his battery and the concealed point beneath the airship. The observer in the airship, of course, signals the engineer officer, the exact point or time when the airship is directly above, and this gives him the correct angle. The guns of the battery are then directed and fired so as to reach the concealed point. It is now important to be able to send intelligible signals to the officer in charge of the battery. If the shot goes beyond the mark, the observer in the airship raises the flag above his head, which indicates that it was too high. HOW USED.--If the shot fell short he would lower the flag. If the shot landed too far to the right, this would be indicated by the flag, and if too far to the left, the signal would, in like manner, be sufficient to enable the gunners to correct the guns. When the exact range is obtained the observer in the ship waves the flag about his head, in token of approval. All this work of noting the effect of the shots must be taken while the airship is under fire, and while circling about within visual range of the concealed object below. The officer in charge of the battery, as well as the observer on the flying craft, must be equipped with powerful glasses, so the effect of the shots may be noted on the one hand, and the signals properly read by the officer on the other hand. It may be said, however, that air battles have not been frequent and that they have been merely incidents of the conditions under which they were operated. The mission of the aeroplane is now conceded to be purely one of observation, such as we have described. Both French and German reports are full of incidents showing the value of observations, and also concerning the effects of bombs. Extracts from the diaries of prisoners gave many interesting features of the results of aeroplane work. CASUALTIES DUE TO AEROPLANES.--In the diary of one was found the remark: "I was lucky to escape the bomb thrown by a French aviator at Conrobet, which killed eight of my companions." Another says: "The Seventh Company of the Third Regiment of the Guard had eight killed and twenty-two wounded by bomb from a French aeroplane." Another: "An officer showed us a torn coat taken from one of sixty soldiers wounded by a bomb from an aeroplane." A prisoner says: "Near Neuville an aeroplane bomb dropped on a supply train, killed four men, wounded six, and killed a considerable number of horses."