152 
MINUTES OF PROCEEDINGS OF 
Mr. Kirkaldy’s 56 th concluding observation on experiments on 
wrought-iron and steel is :—• 
“Iron is injured by being brought to a white, or welding heat, if not at the 
same time hammered or rolled.” 
My own experience corroborates these views. While employed in 
the duty of inspecting the conversion of guns at Elswick, on Major 
PalliseFs system, a portion of one of the tubes got accidentally over¬ 
heated, and the fault was not discovered until the tube was tested by 
water pressure of 3 tons to the inch before being put into the gun. It 
then broke into two pieces, and on examination the fracture was found 
to be largely crystalline, as described above by Dr. Percy. 
There is another objection, which must always hold good against 
these very thick coils. It is claimed in the Armstrong system that, if 
the interior of a coil be cooled more quickly than the exterior—and 
that is always done by water from the centre during the building up of 
the gun—the interior will be in a state of compression, while the 
exterior is in a state of extension, so that a more regular succession of 
tension obtains than by steps from coil to coil. The increased tempera¬ 
ture from which the coil is cooled after forging, will make this law act 
more powerfully in the case of the Fraser coil. It will cool from both 
outside and inside; so that both outside and inside are in a state of 
compression, while the interior is in a state of extension. The ten¬ 
dency is thus to separate into two cylinders, the outer of which will 
not support the inner. 
This tendency is very much increased if, after once cooling as above, 
it be again heated and cooled; for the second heating commences at 
the surface, and causes it to swell out before the interior is softened. 
The internal extended portion remains as it was, and, on the whole 
mass again cooling from the surfaces, the bad effects double themselves. 
I have seen a case of this. A large Morrison hammer was being made. 
A Saturday night intervened, and it was allowed to cool in a half- 
finished state. On Monday it was again heated and completed, but on 
being turned, it was found to contain a hole in the interior so large 
that it had to be condemned. This second heating happens in the thick 
Eraser coil; for the trunnion-piece, with its fore and after coil, having 
been made separately, are all allowed to cool. They are then joined 
together, all heated a second time, and welded into one piece. 
If we consider all these various objections, it is not surprising that 
one of these guns should have burst at proof. 
/3. Pattern with hoo External Coils. 
Eraser* s latest pattern, Fig. 13, is perhaps as good a pattern as is 
ever likely to be arrived at for 9-inch guns, unless the system which I 
am about to propose, and which introduces an entirely new principle, 
be adopted. It has no prominent faults. All the difficulties are so 
evenly balanced, that it is hardly possible to improve on it. Hone of 
them are, however, removed, and any serious fault in manufacture 
might bring one or other into prominent play. Instead of the thick 
