ARTIFICIAL FLIGHT. 551 



achieved l)y Professor Langley, which have been chronicled 

 by the press, have consisted chielly in the construction of a 

 machine, driven by a motor, which has kept its balance con- 

 tinuously for a long flight. His model is not large enough to 

 carry a man, and in the figures which appeared in the Ameri- 

 can papers, the addition of a person standing in the bows must 

 be regarded as artistic licence. 



(iv.) Steering arrangements need but little notice here. 

 Lilienthal and Pilcher and other experimenters on gliding 

 flight have acquired considerable skill in guiding their 

 machines by balancing alone, and it is noteworthy that 

 Lilienthal's fatal experiment was his first attempt at using 

 a movable rudder. If aerial machines should ever be 

 constructed on a large scale balancing will, of course, be 

 out of the question, and horizontal and vertical rudders of 

 some kind will be necessary, and it may be advisable that 

 they should be experimented with soon. 



(v.) Strength and rigidity, unlike the last conditions, are 

 qualities with which all engineers are familiar. In the case 

 of a flying machine this factor introduces peculiar difficulties 

 as Maxim was not slow to discover. In order to keep a 

 flat surface of considerable extent rigid, numerous struts 

 and stays are required, and these Maxim finds add 

 enormously to the resistance of the air at such speeds as 

 are required for flight. Curved surfaces, as every mathe- 

 matician knows, are better in this respect than plane ones. 

 The only way of overcoming the difficulty seems to be to 

 make the machine as small and compact as possible, and 

 here the advantage of superposed planes becomes evident. 

 Thus the conditions of rigidity are in no way antagonistic to 

 the other conditions before enumerated. It is evident on the 

 other hand that want of rigidity, by allowing the aeroplanes to 

 bend, might considerably modify the stability of the machine. 



In this connection I would call attention to the recent 

 progress in kite flying since the subject was first taken up 

 scientifically by Captain Baden-Powell in this country. 

 Professor Hargrave in New South Wales, and others, which 

 has resulted in the discovery that a box with open ends 

 forms a most efficient kite, possessing far greater rigidity 



