ad been
lost.

[Illustration: Figure 40.--Geneva stop mechanism first used in Geneva
watches to prevent overwinding. The starwheel B had one convex surface
(_g-f_, dotted) so the wheel could be turned less than a full
revolution. After Robert Willis, _Principles of Mechanism_ (London,
1841, p. 266).]

The name for the Scotch yoke seems to be of fairly recent origin, the
linkage being called by a Scotsman in 1869 a "crank and slot-headed
sliding rod" (fig. 41). I suppose that it is now known as a Scotch yoke
because, in America at least, a "Scotch" was a slotted bar that was
slipped under a collar on a string of well-drilling tools to support
them while a section was being added (fig. 42).

[Illustration: Figure 41.--Scotch yoke, described as a "crank and
slot-headed sliding rod." From W. J. M. Rankine, _A Manual of Machinery
and Millwork_ (ed. 6, London, 1887, p. 169).]

[Illustration: Figure 42.--A "Scotch" supporting the top member of a
string of well-drilling tools while a section is being added, 1876. From
Edward H. Knight, _Knight's American Mechanical Dictionary_ (New York,
1876, p. 2057).]

It was surprising to me to find that the Ackermann steering linkage,
used today on most automobiles, was patented in 1818 when Detroit was
still a frontier town.[107] Furthermore, the man who took out the patent
described himself as Rudolph Ackermann, publisher and printseller. I
thought I had the necessary clue to the linkage's origin when I noticed
that the first English translation of the Lanz and Betancourt treatise
was published by Ackermann, but the connection finally proved to be more
logical, if less direct. Ackermann (1764-1834), son of a Bavarian coach
builder, had spent a number of years designing coaches for English
gentlemen in London, where he made his home. One of his more notable
commissions was for the design of Admiral Nelson's funeral car in 1805.
The Ackermann steering linkage was not actually Ackermann's invention,
although he took out the British patent in his name and promoted the
introduction of the running gear of which the linkage was a part (fig.
43). The actual inventor was Ackermann's friend George Lankensperger of
Munich, coachmaker to the King of Bavaria. The advantage of being able
to turn a carriage around in a limited area without danger of
oversetting was immediately obvious, and while there was considerable
opposition by English coachmakers to an innovation for which a premium
had to