426 
MINUTES OF PROCEEDINGS OF 
The nature of the gun is also marked on the sight bar, otherwise the wrong 
sight might be used—for the bars are the same in section for all natures. 
At the top of the bar is a gun-metal cross-head, at an angle complemental 
to the deflection, in order that it may be horizontal when in the gun. In 
the cross-head is a sliding leaf with a side motion, for the purpose of giving 
a regular allowance for wind blowing across the range, one wheel being 
higher than another, &c. The barrel head on the old pattern answered the 
same purpose, but the new pattern is simpler and cheaper, and not as liable 
to get out of order. 
The tangent scales are set at the required elevation by means of a gun- 
metal movable clamp, which admits of the sight being taken to the light 
for the purpose. 
The centre hind sight —a short scale for use at close quarters and moderate 
ranges—is of gun-metal. It is six sided; one of its sides has a degree scale, 
the other sides are marked with range and fuze scales for full and battering 
charges in all cases of guns for which there is sufficient data. It works in 
a gun-metal socket, fixed in the gun and provided with a set screw. 
The trunnion sights 3 as also the centre fore sights, are known as the 
"drop" pattern, which consists of a pillar, collar, and socket of gun-metal, a 
leaf of steel, and screw for fixing the leaf. The socket is permanently fixed 
in the gun, and the pillar and collar each lock into it with a bayonet joint; so 
that when once the sight is in its true position, it cannot be removed without 
first raising the collar and turning the pillar round a quarter of a circle. 
The advantages of the “drop” over the “screw” pattern (used in field 
guns), is that the former can be easily removed for transit, and afterwards 
replaced in its true position without any trouble. 
The exposed gun-metal portions of all the tangent and drop sights are 
protected from the influence of the atmosphere by “ bronzing,” the mixture 
of which consists of— 
Bichloride of platinum (Pt, Cl 2 ). 2 parts 
Corrosive sublimate (Hg, Cl). 1 „ 
Vinegar. 1 „ 
The steel bar, leaf, &c. are “ blued ” for the same reason. This is easily 
effected by polishing the surface of the article, and heating it in a sand bath 
until it assumes a blue color, and then allowing it to cool naturally. 
In naval service a wood scale is used in connection with the ship's 
pendulum, for giving elevation or depression w r hen the object aimed at 
cannot be seen from the gun. The scale is square in section, and is 
graduated for degrees and for yards, both for full and battering charges. 
When it arrives on board, it is cut so that when placed upright on the 
naval slide, the zero of the scale corresponds to the zero of the graduations 
(3-| 0 elevation or depression), on the rear face of the cascable, the gun being 
parallel to the deck. It is provided with a movable slide, fitted with a 
pointer and clamping screw; this can be set at the required elevation or 
depression, and must coincide with the degree on the cascable which 
corresponds with the heel of the ship (see Changes in Patterns, §§ 1477-8). 
The graduations on this scale are computed with a radius equal to distance 
between the rear face of cascable and the axis of the trunnions. 
Turret guns were laid in a similar manner, but the allowance for heel 
was obtained, not from a ship's pendulum, but from the number of degrees 
