Elements of descriptive geometry, with applications to isometric projection and othe forms of one-plane projection; a text-book for colleges and ingineering schools by O. E. Randall.

CHAPTER IV

NOTATION
63. To distinguish between a point in space and its projections
on H and V, the point itself will be represented by the capital
letter and its projection by the small letter.
64. The horizontal and vertical projections of a point, as M, will
be represented by m, and m' respectively, and will be read m sub
one and m prime one respectively.
65. If a point, as M, is made to occupy several positions in the
same problem, its horizontal and vertical projections will be represented in order by m,, m'; m,,, m"; m,,, l; etc.
66. When two or more points are projected into the same point,
the letters of all the points will be written upon this common
projection.
67. If a point, as M, is revolved into H, its revolved position
will be represented by m, and the vertical projection of the point
in this revolved position will be represented by m'.
68. If a point, as M, is revolved into V, its revolved position
will be represented by ml, and the horizontal projection of the
point in this revolved position will be represented by m,.
69. The horizontal projection of a vertical projection, as m', will
be represented by (m'),.
70. The vertical projection of a horizontal projection, as ml,
will be represented by (m,)'.
71. If a point, as M, is projected upon a plane, as T, other than
H or V, this projection will be represented by 1MT, and the horizontal and vertical projections of this projection will be represented
by mt, and mt' respectively.
72. If a point, as M, is projected upon a plane, as P, and if this
projection is projected upon another plane, as Q, the last projection
will be represented by MPQ, and its horizontal and vertical projections will be represented by npq, and mpq' respectively.
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