In his works in Paris, for example, M. Blériot employs a skilled staff of draughtsmen, who are busy every day upon designs for new machines. He must keep pace with his rivals, and he must meet the growing demands of the military service. Faster and more reliable machines are demanded every day, and strenuous efforts must be made to fulfil these demands. Therefore, the expense of running an aeroplane factory is exceptionally high. These facts are interesting, as they explain why "a few bits of stick and canvas, and an engine," as an aeroplane has been described, should cost as much as £1000. It is not so much the wood, and the canvas, and the engine that the purchaser is paying for, as the months, and perhaps years, of patient toil and ceaseless expense, which have gone to the production of a practical machine. High prices are charged for aeroplane engines. Here, again, the same causes are at work. Most costly are the preliminary expenses connected with the production of a new petrol engine. In the case of the famous "Gnome," for instance, many thousands of pounds were spent upon a series of experimental engines, before a reliable model could be obtained. II. Economy of a large military order for machines—The incidental expenses. The idea has been conveyed, by the previous notes, that the aeroplane is an expensive machine. So it is, at present, so far as the private purchaser is concerned—although its champions are already prone to point out that a first-class flying machine does not cost more than a high-powered, luxurious motor-car. When the aeroplane is regarded as a weapon of war, however, it should not be considered expensive. It is, in fact, remarkably cheap, particularly when compared with the cost of other forms of armament. The prices, previously quoted, as representing the cost of the best makes of aeroplane, have been for individual machines; and this introduces a point which is greatly in favour of any War Department, when it seeks to equip itself with a number of aeroplanes. Through placing orders for a batch of machines, instead of buying one here and there, any Government should be able materially to reduce the price of any make. Grant, for the sake of argument, that a country decides to provide itself with a fleet of a hundred war aeroplanes. The policy, in such a case, would be to look round, at the beginning of any flying season, and make a selection, say, of the three types of machine best suited for the tasks arising in military work.