t by people like us, no
less intelligent and no less subject than we are to environment, to a
subjective way of looking at things, and to a heritage of ideas and
beliefs.

I have selected the period from the time of Watt because modern
mechanisms originated with him, and I have emphasized the first century
of the period because by 1885 many of the ideas of modern kinematics of
mechanisms were well developed. Linkages are discussed, to the virtual
exclusion of gears and cams, because much of the scholarly work in
kinematic synthesis is presently directed toward the design of linkages
and because linkages provide a convenient thread for a narrative that
would have become unnecessarily complex if detailed treatment of gears
and cams had been included. I have brought the narrative down to the
present by tracing kinematics as taught in American engineering
schools, closing with brief mention of the scholarly activity in
kinematics in this country since 1950. An annotated list of additional
references is appended as an encouragement to further work in the
history of the subject.

James Watt, Kinematic Synthesist

James Watt (1736-1819), improver of the steam engine, was a highly
gifted designer of mechanisms, although his background included no
formal study of mechanisms. Indeed, the study of mechanisms, without
immediate regard to the machines in which they were used, was not
introduced until after Watt's important work had been completed, while
the actual design of mechanisms had been going on for several centuries
before the time of Watt.

Mechanisms that employed screws, cams, and gears were certainly in use
by the beginning of the Christian era. While I am not aware of
unequivocal evidence of the existence of four-bar linkages before the
16th century, their widespread application by that time indicates that
they probably originated much earlier. A tantalizing 13th-century sketch
of an up-and-down sawmill (fig. 1) suggests, but does not prove, that
the four-bar linkage was then in use. Leonardo da Vinci (1452-1519)
delineated, if he did not build, a crank and slider mechanism, also for
a sawmill (fig. 2). In the 16th century may be found the conversion of
rotary to reciprocating motion (strictly speaking, an oscillation
through a small arc of a large circle) and vice versa by use of linkages
of rigid members (figs. 3 and 4), although the conversion of rotary to
reciprocating motion was at that time more frequently