rt reproduced.[91]

[Footnote 91: Jacob Bigelow, _Elements of Technology_, ed. 2, Boston,
1831, pp. 231-256; Olinthus Gregory, _A Treatise of Mechanics_, 3 vols.,
ed. 3, London, 1815.]

A translation of the work of Lanz and Betancourt[92] under the title
_Analytical Essay on the Construction of Machines_, was published about
1820 at London by Rudolph Ackermann (for whom the Ackermann steering
linkage was named), and their synoptic chart was reprinted again in 1822
in Durham.[93] In the United States, _Appleton's Dictionary of
Machines_[94] (1851) adopted the same system and used the same figures.
Apparently the wood engraver traced directly onto his block the figures
from one of the reprints of Lanz and Betancourt's chart because the
figures are in every case exact mirror images of the originals.

[Footnote 92: Rudolph Ackermann, _Analytical Essay on the Construction
of Machines_, London, about 1820, a translation of Lanz and Betancourt,
_op. cit._ (footnote 64).]

[Footnote 93: Thomas Fenwick, _Essays on Practical Mechanics_, ed. 3,
Durham, England, 1822.]

[Footnote 94: _Appleton's Dictionary of Machines, Mechanics,
Engine-Work, and Engineering_, 2 vols., New York, 1851 ("Motion").]

In the _Dictionary of Engineering_[95] (London, 1873), the figures were
redrawn and dozens of mechanisms were added to the repertory of
mechanical motions; the result was a fair catalog of sound ideas. The
ferryboat still tugged at its anchor cable, however.[96] _Knight's
American Mechanical Dictionary_,[97] a classic of detailed pictorial
information compiled by a U.S. patent examiner, contained well over
10,000 finely detailed figures of various kinds of mechanical
contrivances. Knight did not have a separate section on mechanisms, but
there was little need for one of the Hachette variety, because his whole
dictionary was a huge and fascinating compendium of ideas to be filed
away in the synthetic mind. One reason for the popularity and usefulness
of the various pictorial works was the peculiar ability of a wood or
steel engraving to convey precise mechanical information, an advantage
not possessed by modern halftone processes.

[Footnote 95: E. F. and N. Spon, _Dictionary of Engineering_, London
1873, pp. 2421-2452.]

[Footnote 96: _Ibid._, p. 2447.]

[Footnote 97: Edward H. Knight, _Knight's American Mechanical
Dictionary_, 3 vols., New York 1874-1876.]

[Illustration: Figure 36.--Typical mechanisms from E. F. and N. Spon,