l reader a glimpse of the most powerful
tool for kinematic synthesis that has yet been devised; namely,
kinematic analysis, in which the argument is confined to the relative
displacements of points on links of a mechanism, and through which the
designer may grasp the nature of the means at his disposal for the
solution of any particular problem.

As remarked by Reuleaux a generation later, there was much in Professor
Willis's book that was wrong, but it was an original, thoughtful work
that departed in spirit if not always in method from its predecessors.
_Principles of Mechanism_ was a prominent landmark along the road to a
rational discipline of machine-kinematics.

A phenomenal engineer of the 19th century was the Scottish professor of
civil engineering at the University of Glasgow, William John MacQuorn
Rankine. Although he was at the University for only 17 years--he died at
the age of 52, in 1872--he turned out during that time four thick
manuals on such diverse subjects as civil engineering, ship-building,
thermodynamics, and machinery and mill-work, in addition to literally
hundreds of papers, articles, and notes for scientific journals and the
technical press. Endowed with apparently boundless energy, he found time
from his studies to command a battalion of rifle volunteers and to
compose and sing comic and patriotic songs. His manuals, often used as
textbooks, were widely circulated and went through many editions.
Rankine's work had a profound effect upon the practice of engineering by
setting out principles in a form that could be grasped by people who
were dismayed by the treatment usually found in the learned journals.

When Rankine's book titled _A Manual of Machinery and Millwork_ was
published in 1869 it was accurately characterized by a reviewer as
"dealing with the _principles_ of machinery and millworks, and as such
it is entirely distinct from [other works on the same subject] which
treat more of the practical applications of such principles than of the
principles themselves."[73]

[Footnote 73: _Engineering_, London, August 13, 1869, vol. 8, p. 111.]

Rankine borrowed what appeared useful from Willis' _Principles of
Mechanism_ and from other sources. His treatment of kinematics was not
as closely reasoned as the later treatises of Reuleaux and Kennedy,
which will be considered below. Rankine did, however, for the first time
show the utility of instant centers in velocity analysis, although he
ma