When we had become "apt," we were promoted to a course in aeroplane construction. This is an extremely technical course, and at first we were asked to know only simple subjects, such as the incidence of the wings, the angle of attack of the cellule, the carrying force of the tail in reference to the size of the propeller. By the incidence of the wings is meant their upward slope. This is an extremely important matter, for the stability and climbing propensities of the machine depend entirely upon their model. The angle of attack of the cellule is the angle of the different wings in reference to each other. For instance, the incidence of one side must be greater than that of the other on account of the rotary movement of the propeller. There are also certain fixed ratios between the upper and lower planes. Still more important is the carrying power of the tailplane, for if it has too much incidence it lifts the rear end and makes the machine dive, while if it has too little the reverse happens. If any part of the aeroplane is not correctly regulated it becomes dangerous and difficult for the pilot to control. All this becomes more important as one reaches the close of the apprenticeship. One then appreciates this intimate knowledge acquired at the school. Often a pilot is compelled to land in a field many miles from his base. If something is wrong with his motor he must be able to find out immediately what the trouble is, for if a part is broken the camp must be called up on the telephone, so that a new piece may be sent to the spot by motor, with a mechanic to adjust it. When a pilot starts on a cross-country trip he is always given blank requisitions, signed by his commanding officer. When he is forced to land he therefore is able to call upon authorities, whether military or civilian, for any service or assistance he may need, and this "scrap of paper" is sufficient in every case to obtain food, lodging, and even transportation to the nearest aviation headquarters for both the pilot and his machine. [Illustration: The little café across the road]