404 DR PETTIGREW ON THE PHYSIOLOGY OF WINGS. 



The favourite idea with most is the wedging forward of an inclined plane 

 upon the air by means of a " vis a tergo" 



The inclined plane may be made to advance in a horizontal line or made 

 to rotate in the form of a screw. Both plans have their adherents. The one 

 recommends a large supporting area extending on either side of the weight to 

 be elevated, the surface of the supporting area making an all but inappreciable 

 angle with the horizon, the whole being wedged forward by the action of vertical 

 screw propellers. This was the plan suggested by Henson and Stringfellow, 

 and partly carried out by the latter. 



Wenham * has advocated the employment of superimposed planes, with a 

 view to augmenting the support furnished while it diminishes the horizontal 

 space occupied by the planes. These planes Wenham designates Aeroplanes. 

 They are inclined at a very slight angle to the horizon, and are wedged forward 

 either by the weight to be elevated or by the employment of vertical screws. 

 Wenham's plan was adopted by STRiNGFELLOwt in a model which he exhibited 

 at the Aeronautical Society's Exhibition, held at the Crystal Palace in the 

 summer of 1868. 



The subjoined woodcut (fig. 52), taken from a photograph, gives a very good 



Fig. 52. 



idea of the model in question, a b c representing the superimposed planes, d the 

 tail, and e f the vertical screw propellers. 



The superimposed planes (a b c) in this machine contained a sustaining area 

 of 28 square feet in addition to the tail (d). 



■ Its engine represented a third of a horse power, and the weight of the whole 

 (engine, boiler, water, fuel, superimposed planes, and propellers) was under 12 

 lbs. Its sustaining area, if that of the tail (d) be included, was something like 

 36 square feet, i.e., 3 square feet for every pound — the sustaining area of the 

 gannet (p. 385), it will be remembered, being less than one foot of wing for 

 every two pounds of body. 



* On Aerial Locomotion, by F. H. Wenham, Esq., World of Science for June, 1867. 

 t Flying Machines, by F. W. Beeabt, Esq., Popular Science Review for January, 1869. 



