ON A COMPRESSED-AIR FLYING-MACHINE. 55 



is not a necessity for this class of investigation as the engine of the 

 machine is an air-pump itself if its action is reversed and the wing^ 

 levers are used as pump handles. This is a distinct advantage in 

 using compressed air as a motive power which is not to be lightly 

 ignored, as it is obvious that instances could be cited where coal 

 mines, gas-works and water would not be available for restoring 

 the power to the machine. 



Attention is called to the starting gear as being very simple 

 and effective, it has a spring to the cock handle which opens it 

 the desired amount when the toggle that keeps it shut is with- 

 drawn ; the left wrist is passed through the becket of the toggle. 

 This arrangement has never failed to produce a perfect start. 



It is thought that much useful work has been lost to us by 

 experimenters loading their apparatus with devices to save them 

 from damage, and artistic conceits to show where the passengers 

 are to be seated in ornamental cars with flags <fcc. It should be 

 remembered that flying machines are only to battle with the air, 

 and not for knocking down fences or ploughing up the ground. 

 It is not usual to proportion the scantling and plating of ships so 

 that they will stand beating on rocks and sand, but only to safely 

 resist the strains produced by the winds and waves. Perhaps 

 much of the writer's success has been due to the avoidance of this 

 fault, although it is somewhat of a trial to see a month's work 

 knocked out of all shape in a moment. 



This last machine is the first departure from previous practice 

 in this respect, as it has a stick lashed under the receiver and 

 projecting about sixteen inches before the engine, so that when the 

 machine comes to earth the stick is broken and the engine and 

 receiver are less injured than they would be otherwise. There has 

 been no material damage done although seven wrecks are recorded; 

 on the eighth flight as is usual in a successful trial, the machine 

 escaped with hardly a scratch. Some of the wrecks are believed 

 to have been due to the centre of gravity being too high, so the 

 sides of the body plane have been made to slope upwards ; this 

 has the advantage of checking any tendency to slue by opposing 

 some considerable lateral resistance. 



In spite of past experiences the percentage of area in advance 

 of the centre of gravity has been made as much as 30% of the 

 whole area, but continued disaster caused its reduction to 23*3%: 

 it is so difficult to force the mind to believe what seems unreason- 

 able. In fact to show that a large part of the tail area is absolutely 

 useless, a crossbow model of this machine, as it was at the seventh, 

 trial, seemed perfectly balanced, and yet when the paper surface 

 A B C D, Plate I., was cut out it was still in equilibrium 

 although 41*8% of the area was in advance of the centre of gravity. 

 There is much to be learnt here, it seems as if the centre part of 



