76 THE POPULAR SCIENCE MONTHLY. 



whole energy may be used in propulsion alone. Now some may 

 think they see in this a solution of the problem. They will say, 

 " Why not sustain the machine by gas, so that the whole energy 

 may be expended in propulsion alone ? " I answer, that in pro- 

 portion as the balloon principle is added to the flying principle, 

 in the same proportion is size increased ivithout corresponding 

 increase in poiuer ; and therefore in the same proportion is in- 

 creased the resistance of the air to propulsion, and, what is worse, 

 in the same proportion is our machine at the mercy of winds. 

 But it will be objected : " See the fishes, how they swim ! They 

 are not at the mercy of currents. They float suspended in the 

 water — they dart forward against currents — they ascend cascades 

 and leap waterfalls ; in a word, they are largely independent of 

 water-currents. Now suppose we make a machine exactly the 

 shape of a fish, tail and all ; then, by the addition of gas, make it 

 the same specific gravity as the air ; then, by machinery, make it 

 wiggle its tail in the manner of a fish. Where is the difference ? 

 Why may we not make an aerial swimming-machine, if not a true 

 flying-machine ? " Doubtless it is in this direction that we must 

 seek the partial solution of the problem, not indeed of flying, but 

 of aerial navigation. Yet the answer to the extravagant expecta- 

 tions expressed above is plain. The fish — its bones, muscles, vis- 

 cera, brain — the materials out of which are made machine, fuel, 

 and engineer, are of the same specific gravity as the medium 

 (water) in which it swims. Now, whenever we can find materials 

 out of which to make our machine, fuel, and engineer, which shall 

 have the same specific gravity as the air, then, indeed, we may 

 make a successful swimming-machine which shall be independent 

 of winds. But so long as our materials are six or seven hundred 

 times (wood), or five or six thousand times (iron), as heavy as air, 

 we shall not succeed, because of the enormous dead space filled 

 with gas that we are compelled to use, which adds to the resistance 

 of the air and the power of the winds, without adding anything 

 to the power of propulsion. 



Therefore, we repeat, a pure flying-machine is impossible. All 

 that we can expect — all that true scientists do expect — is, by skill- 

 ful combination of the balloon principle with the true flying prin- 

 ciple, to make aerial navigation possible in moderately favorable 

 weather — in other words, to make a locomotive hcdloon ; or, if we 

 choose so to call it, an aericd swimming-machine. That some- 

 thing really useful of this kind will eventually be made, there can 

 be no reasonable doubt. 



