AVIATION IN PRANCE JOURDAIN. 159 



from now 300 kilometers may be attained. These figures <» are those 

 of M. Painleve, member of the Academy of Sciences. 



There remains to be considered one other important question. It 

 is not enough that machines be inexpensive, for if there be too great 

 risk to safety people will not make use of them. There must be a 

 certain degree of security. I have heard it said : " The aeroplane 

 has made trips all right, but you are at the mercy of your motor. 

 What will happen if your motor fails to spark, a thing which is possi- 

 ble at any moment ? Supj)ose you are flying over a city, what would 

 you do? " The aeroplane, say some persons, should therefore fly only 

 above rivers, plains, and highways. AVliat interest would there be 

 under such limitations? 



As a matter of fact, if the motor stops accidentally, the aeroplane 

 does not fall ; it descends as I have said, along the line of an inclined 

 plane, and the angle at which it will descend depends largely on the 

 perfection of the machine and the skill of the pilot. We can admit, 

 generally, that the ratio of the height of the fall to the course covered, 

 measured on a horizontal projection is about 1 to 7, and within a 

 year the ratio of 1 to 10 will surely be attained. Thus the aeroplane, 

 stopped at a height of 100 meters, has at least five or six hundred 

 meters to descend in, not only directly in front but to the right or 

 the left. The machine will therefore be in the center of a circle of 

 at least a kilometer in diameter. It would be quite extraordinary if 

 a suitable place to land could not be found within such limits. (I 

 do not include the hypothesis of soaring, which is beyond the scope 

 of this discussion.) The answer simply is, that if there is fear of a 

 failure of the motor in crossing over cities one should keep at a 

 reason:able height. * * * 



" Not yet confirmed by experiments. — June, 1909. 



