1 The Birth of Science - MSRI

310 11. The Age-Long Recovery
generally dismissed because that work, apart from extracts contained in
Pappus, is held to have been unknown to Europe until the end of the
nineteenth century, when it was found in Arabic translation. But corre-
spondences between several passages of Galileo — on subjects such as
friction or motion on inclined planes — and closely analogous passages
in Heron not relayed by Pappus should make one suspect that the two
texts were not independent. 76 And obviously, given that even today not
all manuscripts in Italian public libraries have been catalogued, it is ab-
surd to claim exhaustive knowledge of those found in private libraries
four hundred years ago. 77
Galileo’s interest in hydraulic experiments first arose during his Paduan
period; in particular, the work that led Galileo to patent a water-lifting
machine dates from 1593–94. 78
Among the experiments that most interested him in subsequent years
were those relative to the syphon principle and the operation of vacuum
pumps. At the time it was not yet possible to build Ctesibian pumps to
sufficient precision, and in particular they could not be made with metal
cylinders. 79 In these conditions it is easy to imagine that the experiments
that gave Galileo food for thought were primarily those of Hellenistic sci- page 383
entists, described in ancient works. Thus it is not surprising that the the-
oretical conclusions often had the same origin. For example, the explana-
tion for water pumping given by Galileo on the first day of the Dialogues,
76
Some such correspondences are analyzed in [Voicu]. The subject will be discussed at length in
a forthcoming work of mine.
77
In the introduction to [Heron/Carra de Vaux], the editor and discoverer of the Arabic version
of the Mechanics bemoans the obstacles met in mapping the fortunes of manuscripts, “especially
when it comes to Roman libraries”, and says he found references to Greek copies of the Mechanics
(none of which he could locate) in several Roman libraries, in Venice’s Biblioteca Marciana and at
the Escorial. The Venice lead turned out to be false (a copy of the Pneumatics wrongly classified as
the Mechanics), but the other manuscripts seem to have been lost track of.
A holograph of Christopher Clavius, dating from 1579 or 1580 and apparently referring to mathematics
courses he would presumably be teaching at the Collegio Romano, details the mechanics
syllabus as consisting of the “mechanical questions of Heron, Pappus and Aristotle” ([Baldini],
p. 175). Since the document is essentially a list of texts, the explicit reference to Pappus shows that
“Heron” did not mean just the passages of Heron included in Pappus.
78
The patent letter is printed in [Galileo: Opere], vol. XIX, pp. 126–129.
79
See for example [Usher], p. 332, where it is said that the use of metal (cast iron) cylinders in
vacuum pumps is attested from the second half of the seventeenth century. Before that, though
metal was used for other parts of the pump, the cylinder was wooden. Clearly techniques for
metal turning and grinding, needed to make surfaces regular enough to ensure a tight fit between
cylinder and piston, did not regain the level they enjoyed in Hellenistic times until after 1650.
Revision: 1.11 Date: 2003/01/06 07:48:20