ARTIFICIAL FLIGHT. 535 



but the experiments made during" the Franco- Prussian war 

 did not lead to any result. Of a fourth contrivance a 

 model was made by M. Julien, who exhibited it at the 

 Hippodrome ; it was a small model and would not work. 

 That did not prove M. Julien to be wrong, because the 

 model was on too small a scale to give a fair chance of 

 success. If it had been made sufficiently large it would 

 have worked satisfactorily, so the inventor said. 



These old designs appear to us as absurd and grotesque ; 

 but Robertson's Minerva still survives in various forms, 

 and M. Petin has his counterpart in the many promoters of 

 syndicates who even now from time to time issue prospec- 

 tuses of air-ships with first and second class cabins, captain's 

 rooms, engine rooms and saloons. 



It is not much more than a year ago that the prospectus 

 of a bicycle company was adorned with a picture of a man 

 in mid-air on a bicycle, quite as fantastic as any of the 

 illustrations in MM. Sircos and Pallier's work, or in Astra 

 Casira, and a Toronto newspaper lately gave an extra- 

 ordinary figure of the " Cowdon Air Navigating Machine" 

 representing a kind of tramcar surmounted by three cigar- 

 shaped tubes bearing the direction "Washington to New 

 York," which tubes, the inventor imagined, or tried to make 

 others imagine, would lift the car. In viewing such designs 

 as these with the cool calculating eye of science, it will be 

 found convenient for the purpose of a rough and ready 

 test, to notice that air is rather over one-thousandth of the 

 density of water, and the weight of the gas contained in a 

 balloon, beine somewhere about one-fifteenth of that of the 

 air displaced as relatively small. It follows that a balloon 

 will only support in round figures one-thousandth of the 

 weight that would be supported by a ship of the same dis- 

 placement. It is thus easy to sift out many worthless 

 designs by imagining the gas bag to be reduced to one- 

 tenth of its linear dimensions and immersed in water ; in 

 most cases it will be obvious that such a vessel would be 

 utterly inadequate to support the weight of the machine. 

 Another equally useful test is afforded by remembering 

 that balloons will support about one ounce for every cubic 



