OTHER PROPERTIES OF CAST IRON. 18] 
So striking a coincidence, induced a new and 
extended series of experiments, to determine 
whether the elasticity is not generally injured 
with much less than one-third of the breaking 
weight, and the annexed tables show this to be 
the case: some slight injury with very small 
weights is certainly produced; but it admits of 
doubt whether or not it affects the ultimate 
strength of the bar,—at first sight it appeared 
that a weight sufficient to produce a permanent 
set would, if continued, be sufficient to break 
the bar, and that time alone was necessary to 
effect the rupture. 
Mr. Hodgkinson took a different view of the 
case, and conceived that bodies by virtue of 
their elasticity, combined with slight ductility, 
might adjust themselves so as permanently to 
bear a load, nearly sufficient to break them at 
once. He had formed this view from having 
found that in experiments on wrought iron 
wires, torn asunder many times in succession, 
they bore nearly as much the last time as the 
first—See Manchester Memoirs, Vol. 5. 
A phenomenon so curious and interesting led 
to the enquiry. How much will cast iron per- 
