accomplished by
cams and intermittent gearing. Nevertheless, the idea of linkages was a
firmly established part of the repertory of the machine builder before
1600. In fact one might have wondered in 1588, when Agostino Ramelli
published his book on machines,[1] whether linkages had not indeed
reached their ultimate stage of development. To illustrate my point, I
have selected the plate of Ramelli that most appeals to me (fig. 5),
although the book exhibits more than 200 other machines of comparable
complexity and ingenuity.

[Footnote 1: Agostino Ramelli, _Le Diverse et Artificiose Machine_,
Paris, 1588.]

[Illustration: Figure 1.--Up-and-down sawmill of the 13th century. The
guide mechanism at lower left, attached to the saw blade, appears to be
a 4-bar linkage. After Robert Willis, trans. and ed., _Facsimile of the
Sketch-Book of Wilars de Honecort_ (London, 1859, pl. 43).]

[Illustration: Figure 2.--Slider-crank mechanism of Leonardo da Vinci
(1452-1519), redrawn from his manuscript notebooks. A frame saw is
depicted at the lower end of the guides. From Theodor Beck, _Beitraege
zur Geschichte des Maschinenbaues_ (Berlin, 1899, p. 323).]

[Illustration: Figure 3.--Blowing engine by Vanuccio Biringuccio, about
1540, showing conversion of motion of the waterwheel shaft from rotation
to oscillation. From Theodor Beck, _Beitraege zur Geschichte des
Maschinenbaues_ (Berlin, 1899, p. 120).]

[Illustration: Figure 4.--Grain mill, 1588, showing conversion of motion
of the operating bars from oscillation to rotation. Note the
fly-weights, predecessors of the flywheel. From Agostino Ramelli, _Le
Diverse et Artificiose Machine_ (Paris, 1588, pl. opposite p. 199).]

[Illustration: Figure 5.--Machine for raising water. Such a machine was
built in Spain during the 16th century and was operated for some 80
years. From Agostino Ramelli, _Le Diverse et Artificiose Machine_
(Paris, 1588, p. 199).]

There was a vast difference, both in conception and execution, between
the linkages of Ramelli and those of James Watt some 200 years later.
Watt was responsible for initiating profound changes in mechanical
technology, but it should be recognized that the mechanic arts had,
through centuries of slow development, reached the stage where his
genius could flourish. The knowledge and ability to provide the
materials and tools necessary for Watt's researches were at hand, and
through the optimism and patient encouragement of his partner