The tail of the monoplane is a rigid combination of two planes intersecting each other at right angles along a central bamboo pole which extends back 3 feet 5½ inches from the rudder-post, to which it is attached by a double joint, permitting it to move upon either the vertical or the horizontal axis. Although this tail, or rudder, may seem at first glance somewhat complicated in the plans, it will not be found so if the frame of the upright or vertical plane be first constructed, and that of the level or horizontal plane afterward built fast to it at right angles. As with the main plane, the tail is to be covered on both sides with cloth, the vertical part first; the horizontal halves on either side so covered that the cloth of the latter may be sewed above and below the central pole. All of the ribs in the tail are to be stitched in with “pockets,” as directed for the rods of the main plane. The construction of the motor is possible to an expert machinist only, and the aeroplane builder will save time and money by buying his engine from a reliable maker. It is not necessary to send to France for a Darracq motor. Any good gasoline engine of equal power, and about the same weight, will serve the purpose. The making of the propeller is practicable for a careful workman. The illustrations will give a better idea than words of how it should be done. It should be remembered, however, that the safety of the aviator depends as much upon the propeller as upon any other part of the machine. The splitting of the blades when in motion has been the cause of serious accidents. The utmost care, therefore, should be exercised in the selection of the wood, and in the glueing of the several sections into one solid mass, allowing the work to dry thoroughly under heavy pressure. [Illustration: Diagram showing how the layers of wood are placed for glueing: _A_, at the hub; _B_, half way to the tip of the blade; _C_, at the tip. The dotted lines show the form of the blade at these points.]