What has here been said about the storage of energy in weights, and concerning the elements of flight, is all intended to lead up to the important subject of sliding freight downhill upon aeroplanes. It may be asked, How about a calm?
There is no calm for the aeroplane. Give it altitude and it can gain velocity, and velocity gives the wind of flight.
The plan for the transportation of freight is simply this: at each shipping-point a power-house (D, [Fig. 2]) may be established to operate captive balloons. These should be cellular, and should be made to hold gas with little waste. In its action the apparatus would be what might be called an inverted elevator; that is, the steam or water-motor in the power-house would not hoist the freight, but, instead, would pull the balloon down after it had hoisted the freight and discharged it by means of a soaring machine, which will presently be described.
In [Fig. 2] A represents a captive balloon at a height of one thousand feet. B and C represent the courses which would be taken by dirigible aeroplanes or soaring machines bearing loads of freight.
Perhaps this seems fanciful. Then let it be remembered that the feat of safely sliding down a long and gentle incline upon an aeroplane has already been performed by Otto Lilienthal, of Steglitz, Prussia. His experiments were illustrated and described in the Berlin Illustrirte Zeitung of Oct. 7, 1893, and one of the drawings—all of which were correctly made from instantaneous photographs—is here reproduced on the first page of [cover]. An improvement upon Lilienthal’s device may be made by adding a pendulum.[1]