Gunnery LEVEL, for levelling cannons and mortars, consists of a triangular brass plate, about four inches high, (fig. 9.) at the bottom of which is a portion of a circle, divided only into 45 degrees; as this number is sufficient for the highest elevation of cannons and mortars, and for giving them the greatest range. On the centre of this segment of a circle is screwed a piece of brass, by means of which it may be fixed or screwed at pleasure. The end of this piece of brass is made so as to serve for a plummet and index, in order to show the different degrees of elevation of pieces of artillery. This instrument has also a brass foot, to set upon cannons or mortars, so that when those pieces are horizontal, the instrument will be perpendicular. The foot of this level is to be placed on the piece to be elevated, in such a manner, as that the point of the plummet may fall on the proper degree; this is what they call levelling the piece.