RECENT AERONAUTICAL I'ROGRESS. 127 



Finally we come to that variety of aerial inachiiie which has been 

 adopted ])y most inventors and which .seems to promise the most satis- 

 factory results. I mean what is known as th(^ aeroplane. Sir Hiram 

 Maxim brouyht this prominently forward many years auo. and both 

 he and Professor Lano-ley have ])roved theoretically that it is the most 

 economical form of apparatus; that is to say, that a uiven weight can 

 be supported with less engine ])ower than by other methods. 



Great progress has also been achieved in recent years in this line. 

 Lilienthal pointed out the g-reater efficiency of curved surfaces as com- 

 pared to Hat ones. Phillips and Hargraves experimented further with 

 aerocurves. Considering how nuich more we know about the sul)ject 

 now than when Maxim Hi'st l)uilt his machints it looks as though we 

 might really hear of gi'eat results shortly from America or Australia. 



Our present position is, then, a hoi)eful one. Hallf)ons have been 

 gradually improved until we can practically rely on ])uilding one to go 

 15 miles an hour and probal)ly more. Large flying machines, giving 

 practical experience of their construction, have been 1)uilt. Ciood- 

 sized models have flown well through the air. Gliding machines, bal- 

 anced and controlled by human eti'ort, have been maintained in the air 

 for considerable periods and have descended at very gradual angles. 

 And. what is of the greatest importance, small engines, giving great 

 power for their weight, have steadily improved 3'ear by year, leaving 

 but little for us to desire in this respect. 



All that we require, then, to attain practical flight, is to make a 

 machine only slightly })etter than those already in existence. To 

 accomplish this all that is recfuii'ed is a certain amount of skill and a 

 good deal of monev- 



There has often been a lot of wild speculation about what might 

 happen when flying machines are introduced into everyday life, but it 

 may be worth while considering for one moment what is likely to 

 result, so as to judge whether the matter is one really demanding an 

 effort to accomplish; whether, in fact, '*the game is worth the candle." 



A\ hatever the exact form the apparatus may take, w^e ma}' assume 

 that it will possess certain characteristics. The first of these is that it 

 will travel very fast. There are several reasons for supposing this. 

 Not only nuist it be able to stem ordinary liglit breezes, ])ut to ])C 

 really useful it should be capable of going against any ordinary wind, 

 and to do this at any useful speed implies a rate of lo or 50 miles an 

 hour. Then, high speeds are economical in aerial machines. Lang- 

 ley, by his ela])orate experiments, has shown that the faster our aero- 

 plane is propelled through the air the less force in pro[)ortion is 

 required to sustain it. Again, the air ship, unlike its prototype on the 

 water, is not impeded l)y skin friction, so that the power re(piired to 

 drive it at high speeds does not increase in the same proportion. A 

 bullet can be propelled through the air at inmiense speed, I>ut if it 



