Right About, is when the soldier completely changes the situation of his person, by a semi-circular movement to the right.
Left About, is when the soldier changes the situation of his person by a semi-circular movement to the left.
ABREAST, a term formerly used to express any number of men in front. At present they are determined by Files.
ABRI, Fr. shelter, cover. Etre à l’abri, to be under cover, as of a wood, hillock, &c.
ABSCISSA, in military mathematics, signifies any part of the diameter or axis of a curve, contained between its vertex or some other fixed point, and the intersection of the ordinate.
In the parabola, the abscissa is a third proportional to the parameter and the ordinate.
In the ellipsis, the square of the ordinate is equal to the rectangle under the parameter and abscissa, lessened by another rectangle under the said abscissa, and a fourth proportional to the axis, the parameter, and the abscissa.
In the hyperbola, the squares of the ordinates are as the rectangles of the abscissa by another line, compounded of the abscissa and the transverse axis.
But it must be remembered, that the two proportions relating to the ellipsis and hyperbola, the origin of the abscissas, or point from whence they began to be reckoned, is supposed to be the vertex of the curve, or, which amounts to the same thing, the point where the axis meets it; for if the origin of the abscissa be taken from the centre, as is often done, the above proportions will not be true.
ABSENT, a term used in military returns. It forms a part of regimental reports, to account for the deficiency of any given number of officers or soldiers; and is usually distinguished under two principal heads, viz.