540 SCIENCE PROGRESS. 



tional to the square root of the Hnear dimensions. If, then, 

 a large machine can be made to h'ft itself off the ground, a 

 smaller machine could be more readily made to do so, and 

 this circumstance adds weight to the experiments conducted 

 on a large scale which have brought Mr. Hiram S. Maxim 

 into prominence as an authority on aeronautical matters. 



Maxim used steam power, the fuel used in the furnace 

 being naphtha. This was burned in a very large number 

 of burners (700 or more), so arranged as to give the largest 

 possible area of flame. The steam was generated in a 

 water-tube boiler similar to those now used on fast ships. 

 It consisted of an enormously large number of fine tubes, 

 giving the largest production of steam in the smallest space, 

 while as for the engines they were so light that Maxim 

 easily lifted them in his hands. The total weight of his 

 machine was about 8000 pounds, and he reckoned that it 

 did not weigh more than eleven pounds per horse-power. 

 Seeing that birds may weigh 1 50 to 200 pounds per horse- 

 power, it will be admitted that Maxim had sufficient motive 

 power in proportion to weight ; and, what is more con- 

 clusive, he has actually been able to make his machine lift 

 itself from the ground when travelling at about thirty-seven 

 miles an hour. 



In order that there might be no danger of accident it 

 ran on a railway, and outside there was an outer railway, so 

 that as soon as it rose a few inches from the ground it 

 pressed upwards on the outer rails, and should thus have 

 been prevented from becoming uncontrollable. Once, how- 

 ever, when the engine was developing 362 horse-power, the 

 outer rails gave way, and the machine actually did fly. 

 That flight was a very expensive one, as it cost nearly 

 ^1000 to repair the machine, but from a scientific point of 

 view it formed the crowning point of Maxim's experiments ; 

 for after the accident the rails were all torn up, affording 

 proof positive that the machine possessed sufficient power in 

 proportion to its weight not only to lift it into the air, but to 

 bend the bars by which the outer wheels were attached, and 

 to pull up the rails as well. 



Of course, on the other hand, the construction of an 



