be paid, the invention soon "made its way from its own intrinsic
merit," as Ackermann predicted it would.[108]

[Footnote 107: British Patent 4212, January 27, 1818.]

[Footnote 108: Rudolph Ackermann, _Observations on Ackermann's Patent
Moveable Axles_, London, 1819. It was interesting to me to note an
abstract of W. A. Wolfe's paper "Analytical Design of an Ackermann
Steering Linkage" in _Mechanical Engineering_, September 1958, vol. 80,
p. 92.]

[Illustration: Figure 43.--Ackermann steering linkage of 1818, currently
used in automobiles. This linkage was invented by George Lankensperger,
coachmaker to the King of Bavaria. From _Dinglers Polytechnisches
Journal_ (1820, vol. 1, pl. 7).]

The Whitworth quick-return mechanism (fig. 44) was first applied to a
slotter, or vertical shaper, in 1849, and was exhibited in 1851 at the
Great Exhibition in London.[109] Willis' comments on the mechanism are
reproduced in figure 44. I hope that Sir Joseph Whitworth (1803-1887)
will be remembered for sounder mechanical contrivances than this.

[Footnote 109: The quick-return mechanism (British Patent 12907,
December 19, 1849) was perhaps first publicly described in Charles
Tomlinson, ed., _Cyclopaedia of Useful Arts and Manufactures_, London,
1854, vol. 1, p. cxliv.]

[Illustration: Figure 44.--Quick-return mechanism. _Top_, Early
representation of the quick-return mechanism patented by Whitworth in
1849, from William Johnson, ed., _The Imperial Cyclopaedia of machinery_
(Glasgow, about 1855, pl. 88). _Middle_, Sketch by Robert Willis from
his copy of _Principles of Mechanism_ (London, 1841, p. 264), which
"shews Whitworth dissected into a simpler form"; it is as obscure as
most subsequent attempts have been to explain this mechanism without a
schematic diagram. _Bottom_, Linkage that is kinematically equivalent to
Whitworth's, from Robert Willis, _Principles of Mechanism_ (London,
1841, p. 264).]

Mechanisms in America, 1875-1955

Engineering colleges in the United States were occupied until the late
1940's with extending, refining, and sharpening the tools of analysis
that had been suggested by Willis, Rankine, Reuleaux, Kennedy, and
Smith. The actual practice of kinematic synthesis went on apace, but
designers often declined such help as the analytical methods might give
them and there was little exchange of ideas between scholars and
practitioners.

The capability and precision of machine tools were greatly enhanced