178 —  Transactions.— Miscellaneous. 
edges of its planes or radii elevated, and as this requires to be turned in an 
opposite direction, therefore the car is kept from rotating. In the model 
there is a crank in each of the axes and at the same height, and each crank 
is connected by a rod to a vertical pedal common to both ; in this manner both 
wheels are compelled to rotate with the same speed but in opposite directions; 
it then follows that by turning only ong. of the cranks by the hand the whole 
apparatus would by reaction be gtiided in azimuth when required. In order = 
to apply any power or force we must have a basis or part which acts as a 
fulcrum wherein action and reaction can have full sway. In birds and all | 
flying creatures each wing is paired with another. 
the working compartment of this model the attempt has been made . 
to so arrange the parts as to utilize the immense force which the human ~ 
form is so eminently capable of exerting. The machinery is reduced to the 
simplest form, namely the two perpendicular winches between which manual 
power can be. exerted. in a sitting posture. These winches are merely U = x 
shaped bends in the prolonged axes of the tension wheels. Let us consider 
the power that can be exerted by the pull stroke. Itis considered that, in 
rowing, manual power is applied in a very advantageous manne "the... 
feet are firinly planted and the arms and shoulders react from them. n 
will be seen by the model that the feet can be placed on the nearly vertical 
pedal; great force could therefore be exerted by the legs alone: in fact 
great force can be exerted by the human form between two cranks in almost 
every part of the revolution when they go round in opposite directions. It 
is not expected that full manual power can be exerted continuously, as it is 
found that most work is done when there is a short period of rest, as in Xp 
rowing; but it might be expedient to exert full power at some partici 
part of the revolution, hence the present arrangement w eby the feet or 
hands can be used either together or alone, thus avoiding dead points and 
allowing of the hands being used for steering. That far more power can be 
exerted. by the legs than by the arms is easily proved by the faet of the 
weight of the body being raised for a whole day long in scaling mountains, — 
whereas if the arms were to be used in pulling the body up under a ladder 
or an inclined rope, a few minutes would lead to exhaustion; and even if 
à á " ide 
_ the power of the arms alone were used in any other mechanical arrange- 
ment, it would still be fatiguing. The arms working however between two 
vertical cranks allows of power being exerted in four ways; Ist., in pulling 
from the front, as in rowing; 2nd., in pushing in the opposite direction or 
of change is really important from its xA. one set of muscles to rest 
v others are operire; an account of a simple arrangement for varying 
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