It was at one time feared that no fastening could be
got for armor plates, as on the impact of a shot the heads or the nuts
always flew off the bolts. The fracture usually took place just at the
point where the screw-thread terminated. Sir William adopted the bold
course of actually weakening the bolt in the middle of its length by
turning it down, so that the screw stands raised up instead of being cut
into the bolt, and by this simple device he changed the whole face of
affairs, and the expedient applied in other ways, such as by drilling
holes longitudinally down bolts, has since been extensively adopted
where great immunity from fracture is required.
It is, however, for the well-known converted gun that Sir William
Palliser's name will be best remembered. When our smooth-bore cast iron
guns became obsolete they were converted into the rifled compound guns
by a process which led to their being known as Palliser guns. The plan
was to bore out a cast iron gun and then to insert a wrought iron rifled
barrel consisting of two tubes of coiled iron one inside the other.
By the firing of a proof charge the wrought iron barrel was tightened
inside the cast iron casing.
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