391 
THE MECHANISM OF BICYCLES. 
safety bicycles were produced, in order to give those who had been in 
the habit of riding the high machines (where the pedal cranks were 
rigidly attached to the high wheel) some idea of the travel of the 
new machine for each turn of the pedal and the consequent power 
required; for the connection between the pedal and the driving wheel 
and consequently the gear is entirely a matter of leverage. For the 
same length of crank and the same sized wheel just twice the power 
must be applied to overcome the rolling resistance of a machine geared 
to 112 as that required for a gear of 56. It should be noted, however, 
in connection with this, that, owing to the fact that it is found to be 
impossible to make more than one and a half complete revolutions of 
one foot in a second, a bicycle required for high speeds such as are 
required on a racing track must be geared high. It seems superfluous 
to remark that the simple way to finding out the ‘gear'’ of any 
machine is to multiply the diameter of the driving wheel by the 
number of teeth on the large sprocket wheel and divide by the number 
of teeth on the smaller sprocket wheel. 
While looking at this machine (Martini) made by Mr. Hardy, a 
bicycle maker, for whose introduction I, in common with others in this 
room, owe a debt of gratitude to Colonel Watkin, it might be noticed 
that the top stay is made in two pieces so that if required for a lady it 
can be unfastened and the ends folded out of the way. The joint 
(invented by Mr. Liebenrood) is on the differential screw principle. 
The connecting piece is provided with female screw threads at each 
end, which screw off and on the hind and front portions respectively 
of the stay when the connecting piece is given a right-handed turn. 
The threads at each end are of different pitch, that on the hind 
portion being 16 threads to an inch, that on the front being 14 to an 
inch, consequently with one turn the connecting piece moves off the 
hind portion fa inch and on to the front portion fa inch, with the 
result that the two portions of the stay are made to approach each 
other and each turn of the connecting piece brings them into great 
tension and gives the stay greater rigidity. 
Though not required by the ordinary rider this adjustment appears 
to present a decided advantage for certain cases —-first where a 
machine is required to be ridden by either a lady or gentleman; it is 
not treating a lady^s bicycle fairly for a gentleman to ride it without 
this additional strength, secondly for those who hire out machines and 
thirdly in the case of mixed tandems so as to allow either the 
gentleman or the lady to ride in front. 
There appears to be a demand on the part of a number of riders to 
have a machine, the ‘gear’ of which can be altered at will without 
stopping, so that a high gear can be used when on the level and a low 
gear obtained when a high wind or a hill has to be encountered. 
The f Protean 9 geared bicycle is constructed on this principle, it 
being possible to employ one of four different gears as required. 
The arrangement is as follows :—There are two sprocket wheels and 
a chain. The small sprocket wheel is not however fixed to the hub 
of the driving wheel, but is in the form of an annular ratchet wheel. 
