AERIAL NAVIGATION. 393 



have placed the rudder in front, where it proves more effective than 

 in the rear, and have placed the operator horizontally on the machine, 

 thus diminishing by four fifths the resistance of the man's body from 

 that which obtained with their predecessors. In 1900, 1901, 1902 and 

 1903 they made thousands of glides without accidents and even suc- 

 ceeded in hovering in the air for a minute and more at a time. They 

 had obtained almost complete mastery over their apparatus before they 

 ventured to add the motor and propeller. This, in the judgment of 

 the present writer, is the only course of training by which others may 

 hope to accomplish success. It is a mistake to undertake too much at 

 once and to design and build a full-sized flying machine db initio, for 

 the motor and propeller introduce complications which had best be 

 avoided until in the vicissitudes of the winds bird-craft has been 

 learned with gravity as a motive power. 



Now that an initial success has been achieved with a flying ma- 

 chine, we can discern some of the uses of such apparatus, and also 

 some of its limitations. It doubtless will require some time and a 

 good deal of experimenting, not devoid of danger, to develop the 

 machine to practical utility. Its first application will probably be 

 military. We can conceive how useful it might be in surveying a 

 field of battle, or in patrolling mountains and jungles over which 

 ordinary means of conveyance are difficult. In reaching otherwise 

 inaccessible places such as cliffs, in conveying messages, perhaps in 

 carrying life lines to wrecked vessels, the flying machine may prove 

 preferable to existing methods, and it may even carry mails in special 

 cases, but the useful loads carried will be very small. The machines 

 will eventually be fast, they will be used in sport, but they are not to 

 be thought of as commercial carriers. To say nothing of the danger, 

 the sizes must remain small and the passengers few, because the 

 weight will, for the same design, increase as the cube of the dimen- 

 sions, while the supporting surfaces will only increase as the square. 

 It is true that when higher speeds become safe it will require fewer 

 square feet of surface to carry a man, and that dimensions will actually 

 decrease, but this will not be enough to carry much greater extraneous 

 loads, such as a store of explosives or big guns to shoot them. The 

 power required will always be great, say something like one horse 

 power to every hundred pounds of weight, and hence fuel can not be 

 carried for long single journeys. The north pole and the interior of 

 Sahara may preserve their secrets a while longer. 



Upon the whole, navigable balloons and flying machines will con- 

 stitute a great mechanical triumph for man, but they will not ma- 

 terially upset existing conditions as has sometimes been predicted. 

 Their design and performance will doubtless be improved from time 

 to time, and they will probably develop new uses of their own which 

 have not yet been thought of. 



