NEW LIGHTS ON THE PROBLEM OF FLYING. 751 



The outline of the argument, the reader will remember, was as 

 follows : 



1. There is a limit to the size and weight of any locomotive 

 machine, whether natural or artificial. This limit is the result of 

 the law that while the strength of material and force of all kinds, 

 whether by muscular contraction or by steam pressure, increase 

 as the square of the diameter of muscle or of piston, the weight 

 of the machine varies as the cube of the diameter of all parts. 

 Thus with increasing size, weight must quickly overtake and pass 

 beyond strength. This limit varies with the kind of machine. 

 The limit of an efficient walking machine was probably reached 

 in the largest land animals of previous geological times. For a 

 rolling machine like a locomotive engine or a bicycle, where the 

 weight is supported on wheels, or in a swimming machine where 

 the weight is supported by water, and where, therefore, in both 

 cases the whole energy is expended in progression, the limit is 

 much higher ; and, therefore, a locomotive engine and a whale 

 may be heavier than any walking animal. 



2. The limit of weight of a flying machine is very much lower 

 than that of either a swimming, rolling, or a walking machine. 

 The limit of an efficient, manageable flying machine is in fact 

 reached in the largest birds, such as in the condor among long- 

 winged and the bustard among short-winged birds, and to our 

 surprise we find it only about fifty pounds. The condor can barely 

 lift himself from the ground, although when well up he sails with 

 ease and grace. There are, indeed, still larger birds, like the os- 

 trich, but they can not fly. True, their wings are rudimentary, but 

 they have become so only because these birds have passed beyond 

 the flying limit. 



3. Now, a bird is admirably constructed for economy of force. 

 Not only is everything sacrificed to the one supreme object of fly- 

 ing, but the animal machine, using fats and starch for fuel and 

 getting energy through the mechanism of nerve and muscle, is 

 admittedly more economical and efficient i. e., will develop more 

 force and do more work for the same weight of fuel and machine 

 than any artificial machine yet devised. It seems hopeless to sur- 

 pass it. Therefore, the weight of a machine that will be able to 

 lift itself in the air can not exceed fifty or a hundred pounds. 



4. But it is idle to talk of a flying machine with fuel and en- 

 gineer and freight being less than many times this limit. There- 

 fore, a flying machine which is anything more than a toy is im- 

 possible. 



Such is a bare outline of the argument which seemed then 

 and to a large extent seems now irrefutable. But Langley's re- 

 cent experiments certainly put the question in a new and some- 

 what more hopeful light ; and renewed reflection on the whole 



