base-line, to the axes of the trunnions, and to the
connecting piece of the trunnion-square, when its branches rest
against their rear, with the plates across their upper surfaces.

The Inspector will further satisfy himself of the correct tracing of
the line of sight on the gun, by examining the lathe and the manner
of tracing it in the plane of the axis of the bore, at right angles to
the axis of the trunnions, as by it are placed the sights and vent,
and in their absence it serves as a line of metal sight.

The positions of the sight-masses are verified by the profile-board,
and by reference to the line of sight, traced on them; their form and
dimensions by the templates.

The positions of the lock-lugs and their forms are verified by means
of the bronze pattern furnished to each foundry for each class of the
Dahlgren guns, and their dimensions by the templates. For other guns
the position of the lock-piece is marked on the profile-board, and
their measures taken as above.

The opening of the cascabel and its curves, and those of the breech
and the muzzle-swell, are verified by means of the "cylinder-block"
and the templates.

30. The following variations from the proper dimensions may be
tolerated by the Inspector, though every effort should be made to
conform exactly to the drafts furnished by the Bureau of Ordnance.

In the diameter of the bore { more 0.03
{ less 0.00

Exterior diameter { where turned } more .05
{ or planed } less .05
{
{ where not } more .20
{ turned or planed } less .05

In the length { of the bore, more or less .10
{ from rear of base-ring or line to face of
{ the muzzle, more or less .25
{ of the cascabel, from rear of base-ring to
{ the end, more or less .20
{ of the reinforce, more or less .15

From the axis of trunnions to base-line, more or less .05

In the length of chamber, more or less .10

In the position of the axis { above axis of the bore .00
of the trunnions { below axis of the bore .