26 REPORTS ON THE STATE OF SCIENCE.—1918. 
hy San F-00787 n? tan? B feet. 
='0002249 7? tan? 8B métres. 
From a chronograph record, n=139°5 and from the diagram 
3°43 Iiy == 0002249 x 1389°5? x 3°48? 
CS 4:29? 
The loss is represented by h—h.=3—2-797 =0°208 metres. 
In this case the loss due to friction is 68 per cent. 
After impact measure from diagram tan —- and then 
=2°480 métres 
tan B= =2°797 métres. 
0002249 x 139-5? x 5°30? 
7:04? 
Therefore the loss due to rupture of test-piece is 
2°797 —2°480=0°317 métres. 
lf W=12 kilos the total energy absorbed in rupture= 
12 x 0°317=3'804 K.G.M. 
The frictional losses with the 36 kilo hammer were 1°8 per cent. 
Remarks on Impact-Testing Machines. 
The Charpy pendulum hammer is a very suitable machine for testing 
brittle materials, as the swing of the pendulum after impact is greater 
than with less brittle materials. The Guillery machine is a very suitable 
machine for testing tough materials, as the water column descends to a 
greater extent than with less tough materials. 
In both machines the energy of the moving masses at the moment 
of impact is expended in causing the rupture of the test-piece, and in 
producing deformations of the frame of the machine and the anvil, the 
remaining energy in the moving masses is shown by the angle moved 
through by the pendulum, and the fall of the water column in the Charpy 
and Guillery machines respectively. The errors due to the deformations 
of the frame and anvil cannot be easily calculated. If we have a pendulum 
anvil as well as a pendulum hammer, we can find the actual energy 
absorbed by the test-piece, after determining the losses due to friction. 
If the masses representing the pendulum anvil are about twenty times 
the mass of the pendulum hammer, such a machine would give results 
of comparative value which could be used in expressing definitely the 
resilience of the material. Dr. Stanton found that with a pendulum 
anvil the energy of rupture was 5 per cent. lower than in a similar machine 
with a fixed anvil. 
In the direct fall machine such as the one used by the authors, pro- 
vided with the apparatus for the determination of the energy of the 
hammer at the moment of and immediately after impact, the difference 
between these energies is not entirely expended in the rupture of the 
test-piece, but the losses due to deformations of the hammer and anvil 
are relatively small, and, when carefully used, this machine will give 
a 
