By a new system of very simple signs I ultimately succeeded in rendering the most complicated machine capable of explanation almost without the aid of words.
In order thoroughly to understand the action of any machine, we must have full information upon the following subjects, and it is of the greatest importance that this information should be acquired in the shortest possible time.
I. The actual shape and relative position of every piece of matter of which the machine is composed.
This can be accomplished by the ordinary mechanical drawings. Such drawings usually have letters upon them for the sake of reference in the description of the machine. Hitherto such letters were chosen without any principle, {143} and in fact gave no indication of anything except the mere spot upon the paper on which they were written.
〈RULES FOR LETTERING.〉
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.