19]
42. What is an elevating arc, and its use?
It is an arc attached to the rear part of the cheek of a gun-carriage, having its centre in the axis of the trunnions; the arc is graduated into degrees and parts of a degree. By placing the axis of the piece horizontal, and marking the breech at any one of the divisions on the arc, any elevation or depression required will be noted by the number of degrees below or above this mark. It turns on a pivot which admits of the arc, when not in use, being placed inside the cheek to which it is attached.
43. What is the use of the knob of the cascable?
To facilitate the handling of the piece in mounting and dismounting it, and moving it when off its carriage.
44. Of what use are the trunnions of a piece?
By means of them the piece is attached to its carriage; and by being placed near the centre of gravity, it is easily elevated or depressed.
45. What are the dolphins of a piece?
Two handles placed upon the piece with their centres over the centre of gravity, by which it is mounted or dismounted.
46. Are all pieces provided with dolphins?