When we examine the numerous designs that have been proposed for power- driven aëroplanes it is most apparent that the designer, in most cases, has lost sight of the all-important subject of the efficiency of the different parts.

The aeroplanes are often quite large enough to give the required “ lift,” but the “ drift “ is enormous, the propellers are usually far too small in diameter, and the motor is so poorly cooled and adjusted, that it is not capable of giving anything like its rated power.

Any one of these faults is sufficient to make a failure of a possible success, but when they are combined, as they usually are, the machine is hopeless. I have just seen in Paris a machine glaringly wrong even in the most elemental principles, yet the builder had spent a large sum of money for a costly motor and its accessories.