74 THE POPULAR SCIENCE MONTHLY. 



not be so low — in flying-machines. There are forces, they will say, 

 such as steam, electricity, explosions, etc., which are far more 

 powerful than muscular contraction. Especially is electricity 

 looked to in a vague way to do for us many wonderful things, 

 this of flying among the number. Now, this is again a great mis- 

 take. Nerve-energy acting through muscular contraction, and 

 supplied by the combustion of foods, such as oils, fats, starch, 

 sugar and fibrin, together form the most perfect and efficient 

 engine that we know anything of ; i, e., will do more luork with 

 the same iceight of machinery and fuel. 



There was much loose talk a few years ago about condensing 

 and storing electricity in immense quantity, in small space, by the 

 use of Faure's battery. Millions of foot-pounds, it was said, may 

 be thus condensed and stored in a small box and carried about. 

 To the unreflecting, millions of foot-pounds seems a very large 

 quantity. Extravagant expectations were thus raised in the popu- 

 lar mind. I remember at that time talking with a very intelli- 

 gent gentleman on this very subject of flying-machines ; and he, 

 in rebuttal of my argument, suggested the use of stored elec- 

 tricity. " Why," said I, " there is more energy stored in a piece 

 of coal that may be put in the vest-pocket than can be stored in 

 a Faure's battery weighing three hundred pounds ! " Faure's bat- 

 tery is doubtless a good thing, but chiefly, like a fly-wheel, not 

 for increasing the amount but regulating the floiv of force. He 

 then suggested the enormous force of explosives, such as the 

 nitro-compounds. The feeding of these to the engine might, he 

 rightly thought, be so regulated as to supply a continuous force. 

 But here also lurks a fallacy, the result again of a misconception. 

 The force of such compounds is characterized by great intensity 

 rather than great quantity. The whole force is compressed into 

 an almost infinitely small space of time, and therefore very in- 

 tense. But stretch it out as a continuous force and it becomes no 

 greater, probably less, than that of an equal weight of burning 

 coal. There is probably no greater available energy in the world 

 than that produced by the burning of carbon and hydrogen. It 

 is this form of energy that we use in steam-engines ; this we find 

 most powerful and economical in making electricity ; this, also, 

 is what is used in the animal machine. The only question that 

 remains, then, is the relative economy of its use. Now, I think it 

 will be admitted on all hands that no known engine compares in 

 this respect with the animal body. It is acknowledged by me- 

 chanical engineers that the animal machine, burning hydro- 

 carbonaceous food, and acting through nerve and muscle, more 

 nearly approaches the theoretical limit of possible work than 

 any, even the best, steam-engines. More accurately, the animal 

 body is about twice as effective as the best Cornish engine. 



