174 Transactions.— Miscellaneous. 
piece of thin, stiff card-board and cut a cross out of it; a slight obliquity is 
then imparted to the arms or planes, and a piece of wood is cemented 
through the centre to act as a vertical axis; if, then, rotation be imparted 
to it by the finger and thumb, it readily rises to the ceiling of the room. 
Varying the experiments as regards shape, etc., it is found advantageous to 
construct the planes broader towards the circumference; secondly, to bend 
the broad ends or tips somewhat downwards; and, thirdly, to impart a 
slight serew-form to the vanes in imitation of that possessed by a feather. 
The boomerang, used as a missile by the Australian natives, affords an 
example how a horizontal force can be transformed into a lifting force. 
The wheel, here exhibited, has been devised with the idea of securing the 
planes in their true position, especially towards the tips, and of discarding 
all dead weight in those parts near the centre of the wheel where the motion 
of rotation is too slow to assist in elevating it. To effect these, I have 
constructed a horizontal wheel in which the circumference is, as it were, 
the basis or skeleton, and the radii act by tension so as to retain a light 
vertical axis in the centre. In this manner a surprisingly large, strong, 
and light wheel is obtained, the necessary weight of the circumference 
being utilized, as will afterwards be explained. 
Two systems of radii are attached to the circumference of the wheel, 
each system containing eight pairs of tension strings; the tension of all 
these radii can be thus increased simultaneously by simply widening the 
systems on the axis. 
By an inspection of the model, it will be seen that narrow pieces of 
tracing-cloth are attached between each pair of the tension strings; the 
anterior edge of each plane is attached to the upper side of the circum- 
ference, and the posterior edge to the lower side of it. The thickness of 
the rim thus gives the degree of obliquity of the planes, namely, 5° at the 
tips, while the planes are nearly horizontal near the axis. By this 
arrangement the resistance of the air to the motion of the radii is utilized 
in buoying up the wheel; and as the axis can be turned directly by a crank, 
the necessary speed of the circumference can be obtained by simply making ` 
the wheel large enough, thus dispensing with the friction which would arise 
if multiplying wheels were used—size of the wheel forming no theoretical 
objection in the limitless expanse. The waste of power by resistance and 
frietion can be thus reduced to a minimum. 
Though there must be great difficulty in observing the shape and position 
whieh the individual feathers and wings of birds assume while in actual 
flight, yet it is easy to fix them in a current of air and so watch the effect. 
In this way it will be seen that the posterior and thin edge of the feather 
yields more than the other parts in flight, especially towards the tips. The 
