42 NOTES ON FLYING-MACHINES. 
The rough workmanship is found to be of comparative unim- 
portance compared with the adjustment of the planes, but repeated 
failures have brought out a slight improvement in the execution, 
and several interesting results. 
It is necessary to see clearly that these machines are identical 
in principle with the model previously exhibited and described, 
that had two vertical planes that were trochoided in water. The 
plane of the body and tail represents one of the vertical planes, 
and the equivalent plane of the two wings the other. Ata casual 
glance they seem totally dissimilar ;.a closer analysis will make it 
evident that they are one and the same tegen: 
The equivalent plane, as I term it, is an imaginary surface 
trochoided by an imaginary crank and connecting rod, that throws 
a wave equal in section and pitch to the me n of the infinite 
and connecting-rod are embodied in the universal joint of radially 
trochoided planes, but for rough experimental work such as this, 
it has been found most convenient to put the connecting-rod at a_ 
distance from the universal joint sufficiently great to ensure toler- 
ably exact adjustment of the work that I am “capable of doing. 
The experiments show that the greater surface of each plane 
For a same reason, if a boat is towed: on an even keel it is 
difficult to keep her straight—she will yaw, —_ if not met, will 
a greater combined effect than the smaller number of highly 
a oe striking the forward part of the boat, and if the 
she returns of herself to the course, and keeps it. 
pee cert that theafter part of the most efficient trochoided 
ane emg the fo paromsde must Shenstone be closely dependent on 
es to make the two parts” 
this puts a torsional 
