558 KANSAS CITY REVIEW OF SCIENCE. 



die" in such a state of equipoise that a slight force obtained from a vertical screw- 

 would cause it to rise or descend. These requirements were : 



A. A motor distinguished by a greater economy of power than the best hitherto 

 constructed. After the appearance of my article I received from the eminent Chief 

 Engineer of the Erie Railway, Mr. Octave Chanute, Vice-President of the Amer- 

 ican Association of Civil Engineers, carefully prepared tables of the ratios of in- 

 creased atmospheric resistance to increased speed, showing what powerful and 

 economical motors are required to overcome the former. This gentleman also 

 has made experments, by affixing apparatus to railway cars, in order to determine 

 the shape of a moving structure which shaU meet with the least resistance from 

 the air. 



B. A Method of Storing Force, so that it could be applied to the propulsion 

 of the aeronon, with economy of weight, without danger to the structure of ig- 

 nition, and in quantity sufficient for prolonged flight. I wrote that " the electric en- 

 gine will be required. Electricity, in fact, will be as indispensable to the acrobat 

 as to one of Jules Verne's imaginary structures. The electric light will flash from 

 its lookout station and illuminate the inner galleries ; while the steering and pro- 

 pulsion will be governed by electric signals." 



Within this year the marvellous invention of the Faure Accumulator has 

 solved the problem of the Storage of Force, and we are assured that equally sur- 

 prising advances may be expected in its capacity to render a greater amount of 

 energy for the given bulk and weight of the reservoir. 



C. .A cheap process of obtaining aluminum in quantity was yet to be dis- 

 covered. 



I wrote that " lightness and strength" must be the watchword. "All the in- 

 ternal stays, ties, braces, to be made of strong but delicate metallic rods, wire and 

 tubing.^' The following reference was made to the metal best suited for the pur- 

 pose : 



" Some years after I began to think of this subject I fell into conversation with 

 an intelligent machinist, the chance companion of a railway trip. He remarked 

 that he thought that the solution of our problem might depend upon the increas- 

 ed production of aluminum — then a comparatively nev/ metal. 



'•' This, one of the most abundant, of metals, is so difficult of extraction from 

 the clay that the cost at that time was $i.8o per ounce. By 1867 it was obtained 

 through an improved process from cryolite, at a cost of ninety cents per ounce. 

 Recent authorities quote the cost of manufacture as low as $4 a pound. Its spe- 

 cific gravity, when hammered and rolled till strong as iron or stronger, compares 

 with that of iron and copper as 2.67 to 7.78 and 8.78 respectively. It is, there- 

 fore, but one-third 2i% heavy as the lighter of these metals, and even weighs less 

 than glass. There are signs that it will yet be produced so cheaply as to be use- 

 ful for much of the jointed frame work of our structure, and for portions of the 

 machinery not subject to excessive heat. But though it cost its weight in sil- 

 ver it might well be afforded, if by its use a structure could be made to navigate 

 the air. 



