XXX. ABSTRACT OF PROCEEDINGS. 
of the deflections of the rims during rotation are given, so 
that the shape of the rim at any speed within the elastic 
limit of the material can be seen. A set of diagrams is 
given for each of six flywheels, shewing the deflections of 
points round the rims at rising speeds and the deformations 
of the rims at any particular speed. The flywheels tested 
were of different design as follows :—1 Three armed wheel 
straight arms; 2 Four armed wheel straight arms; 3 Four 
armed wheel curved arms; 4 Six armed wheel straight 
arms ; 5 Four armed wheel straight arms, jointed midway 
between the arms; 6 Four armed wheel straight arms, 
jointed along the arms. The curves for the curved armed 
wheel show a large inflection between the arms, the maxi- 
mum deflection being close to the arms. The tests on the 
last two wheels show very clearly the great advantage of 
having the joint along the arms, the effect of the joint in. 
the last wheel being in fact almost negligible. The deflec- 
tions obtained for the straight armed wheels without joints 
are compared with the deflections as calculated by Pro- 
fesssor Lanza’s theory, and a method of finding the equa- 
tions to the curves of the rims is illustrated. A clear 
description of the measuring apparatus is given by which 
a deflection of zzvsooth part of an inch can be measured 
while a wheel is rotating. The speeds are accurately 
measured by means of a chronograph, the revolutions of 
the wheel being recorded on smoked paper together with the 
vibrations of a tuning fork making 100 vibrations per second. 
The physical properties of the material of the wheels were 
determined, tensile tests and transverse tests being made 
on specimens cast with the wheels. The extensions in the 
tensile tests were measured by the Martens’ mirror appar- 
atus and the modulus of elasticity obtained. The deflec- 
tions in the transverse tests were measured by means of a 
microscope, the specimens being tested resting on knife 
