NOTES ON FLYING-MACHINES. 21 



rudders to skates. It is a matter of certainty that if the structure 

 has horizontal motion, and the centre of gravity is moved to one 

 side, the machine will turn to that side ; and if the centre of 

 gravity is moved forward, the machine will plunge downwards. 

 This is quite independent of any mechanism for varying the area 

 of the wings or tail, which will, of course, come to the same thing, 

 but is objectionable, as it increases the number of parts. 



It has been remarked that the wings of these machines differ 

 from birds' wings in having no membrane or web on the portion 

 of their length near the body. If the triangle contained between 

 the forestay, backstay, and strut were covered with paper, and 

 the strut were supposed to have no weight or area, the wing 

 would oscillate about a neutral axis near the middle of the midrib 

 — that is, as the triangular portion of the wing descended the 

 four-sided part would ascend, and the two parts would mutually 

 trochoid one another, each acting and re-acting as the two boats 

 (Fig. 2, Trochoided plane). This would shorten the effective 

 length of the wing, so that material, and consequently weight, 

 is economised by attaching the triangular part of the wing rigidly 

 to the strut, incorporating it, as it were, with the body and tail. 

 The blue and red disks on the wing of the model shew this. A 

 red disk is on the top of the wing near the tip and a blue one 

 underneath, a blue disk is on the top of the wing near the strut 

 and a red one underneath. As the wing descends both red disks 

 are visible, as the wing ascends both blue ones are seen from a 

 position nearly in a line with the axis of the model ; the surfaces 

 with the same colours are thrusting at the same time. This form 

 of machine is not being experimented with, as it is thought to be 

 more easily injured than that shewn in the drawings. 



In birds it is noticeable that the inner portion of the wing does 

 not move through the same angle as the tip, when the wings are 

 up both portions are in a straight line, when the inner part is 

 horizontal the tip is considerably below it, and when the wing has 

 reached its lowest position the outer part is nearly vertical ; it is 

 thought that the identity of the actions of the trochoided plane 

 flying-machine and a flying bird might easily be proved if such an 

 investigation would be of any practical utility. 



It was long doubtful whether an impulse was not unconsciously 

 given to the 24-band models when they were started ; it is now 

 clear they spring from the hand, as several have smashed when 

 the winder was released, and dropped nearly vertically, s*o that 

 the flight is still measured from the starting point. 



Before describing the large machine on wheels, particular 

 attention is drawn to the detail drawing of the 24 band machine 

 (Fig. 8), it embodies all the latest improvements and will well 

 repay a careful scrutiny j it is drawn double size for plainness and 



