Page:The Kinematics of Machinery.djvu/27

Rh after the invention, that therefore reflection and recollection have had time to work upon each other. Watt expressed himself much more directly and distinctly in a letter written in 1784 to Boulton, giving him the first idea of the invention:—

"I have started a new hare," he writes; "I have got a glimpse of a method of causing a piston-rod to move up and down perpendicularly by only fixing it to a piece of iron upon the beam, without chains, or perpendicular guides, or untowardly frictions, arch-heads, or other pieces of clumsiness, by which contrivance, if it answers fully to expectation, about 5 feet in the height of the [engine] house may be saved in 8 feet strokes, which I look upon as a capital saving; and it will answer for double engines as well as for single ones. I have only tried it in a slight model yet, so cannot build upon it, though I think it a very probable thing to succeed, and one of the most ingenious simple pieces of mechanism I have contrived, but I beg nothing may be said on it till I specify." undefined

If we examine the specification referred to we find no less than six methods of guiding described, and among them the very "perpendicular guides" and "arch-heads" found fault with above; two of these methods take the form which our mechanism can assume. One of the six is specially notable,—it is exactly the parallel motion of Reichenbach, and seems to lead up to the motion more generally known by Watt's name. Watt has evidently not recognised this,—and later on it has completely escaped him, at which one cannot wonder, considering the uncouth garb of timber beams and hammered rods in which the elegant mechanism was at that time disguised.

We see that even a thinker like Watt was at fault in the essential elucidation of the matter. Yet we note at the same time that each thought in the inventor's stream of ideas is developed out of another, that the ideas form a ladder up which he presses step by step,—through labour and exertion,—to his goal. His eventual success gains from us the more respect that he did not find the end of his exertions close at hand. But the inspiration, the instantaneous illumination,—cannot be detected;—he says above "and  it occurred to me," which