872 BEPOBT— 1893. 



He says that heavy birds, with relatively small wings, carry about 150 lb. per 

 horse-power exerted, and birds such as the albatross and vulture probably about 

 250 lb. Professor Langley, with small slanting planes, was able to carry 250 lb> 

 per horse-power exerted ; and Mr. Maxim, using heavier weights in proportion to 

 plane-area, 133 lb. per horse-power, and using lighter ones, nearly the same as 

 Professor Langley. 



Mr. Maxim has lately devoted his energies to constructing a motor which 

 should meet the requirements of the case, and has succeeded, he says, in producing 

 one — a steam-engine burning naphtha and with atmospheric condenser, within a 

 total weight of 8 lb. per horse-power. He thinks, however," that by using light 

 naphtha and its vapour in the boiler instead of water, as well as in the furnace as 

 fuel, a weight as low as 5 lb. per horse-power may be reached. 



Meanwhile Professor Langley "s ideas have been embodied in an experimental 

 flying-machine, a drawing and description of which will be found in the ' Daily 

 Graphic ' for July 1, 1893. The body, which resembles that of a bird and is 15 

 feet long, contains the propelling machinery in duplicate. The wings, which 

 are 40 feet across, are of China silk spread on a tubular framework, stiffened with 

 wire trusses. The boilers use liquid fuel and contain a highly volatile fluid. The 

 capabilities of the machine have not yet been practically tested. 



Promising as are the results hitherto obtained, they are as yet far from placing 

 us on a level with birds in power to utilise the atmosphere as a navigating medium. 

 The absolutely necessary power of delicate guiding, in rising, falling, and turning, 

 whatever the direction or force of the wind, has yet to be considered and worked 

 out. What would happen in case of a temporary breakdown of the aero-plane 

 machinery we shudder to think of 



An important step has been efi'ected by the discovery that parachutes with 

 tubular orifices at the top are comparatively safe appliances for descending to the 

 earth from indefinitely high altitudes. Perhaps it may be arranged that each 

 aeronaut should be able, at a moment's warning, to gird himself with one of these 

 as witli a life-belt on board ship, and so descend in safety, or one or more auto- 

 matically opening in case of disaster might be fitted to the aero-plane as a whole. 



EVENTTTAL EXHAUSTION OF FUEL-STJPPLT. 



I have still to refer to one other question, the consideration of which must 

 always give rise to very serious thoughts. We have seen that the decisive vic- 

 tories which, in modern times, man has gained over matter and over other animals 

 have been due to his use of power derived from other than animal sources. That 

 power has invariably proceeded from the combustion and the destruction of fuel, 

 the accumulations of which in the earth are necessarily limited. 



Mechanical appliances, involving the consumption of fuel, have, for a century 

 at least, been multiplying with alarming rapidity. Our minds have been set 

 mainly on enlarging the uses and conveniences of man, and scarcely at all on 

 economising the great sources of power in nature, which are now for the most part 

 its fuels. Terrible waste of these valuable stores is daily going on in almost every 

 department of use. Once exhausted they can never be replaced. They have been 

 drawn upon to some extent for 1,000 years, and extensively for more than 100. 

 Authorities say that another 1,000 years will pxhaust all the more accessible 

 supplies. But suppose they last 5,000 years — what then? Why, then, as far as 

 we can at present see, our only motive-powers will be wind and water and animals, 

 and our only mode of transit, sailing and rowing, driving, cycling, riding, and 

 walking. 



Sir Eobert Ball has estimated that in not less than 5,000,000 and not more 

 than 10,000,000 years the sun will have become too cold to support life of any 

 kind on this planet. Between the 5,000 years when fuel will certainly be ex- 

 hausted and the 5,000,000 years when all life may be extinguished, there will still 

 be 4,995,000 years when, according to present appearances, man will have to give 

 up his hardly-earned victories over matter and other animals, and the latter will 

 again surpass him, each in its own element, because he has no fuel. 



' Engineer, January 13, 1893, p. 28. 



