and in fact gave no indication of anything except the mere spot upon the paper on which they were written.
I then laid down rules for the selection of letters. I shall only mention one or two of them:—
1. All upright letters, as a, c, d, e, A, B, represent framing.
2. All inclined letters, as a, c, d, e, A, B, represent moveable parts.
3. All small letters represent working points. One of the most obvious advantages of these rules is that they enable the attention to be more easily confined to the immediate object sought.
By other rules it is rendered possible, when looking at a plan of any complicated machine, to perceive the relative order of super-position of any number of wheels, arms, &c., without referring to the elevation or end view.
II. The actual time and duration of every motion throughout the action of any machine can be ascertained almost instantly by a system of signs called the Notations of Periods.
It possesses equal facilities for ascertaining every contemporaneous as well as for every successive system of movements.
III. The actual connection of each moveable piece of the machine with every other on which it acts. Thus, taking from any special part of the drawing the indicating letter, and looking for it on a certain diagram, called the trains, the whole course of its movements may be traced, up to the prime mover, or down to the final result.
I have called this system of signs the Mechanical Notation. By its application to geometrical drawing it has given us a new demonstrative science, namely, that of proving that any given machine can or cannot exist; and if it can exist, that it will accomplish its desired object.
