FLUIDITY AND PLASTICITY
PAET I
^ISCOMETRY
CHAPTER I
PRELIMINARY. METHODS OF MEASUREMENT
Introductory.—What one may be pleased to call "dominant
ideas" have so stimulated the work on viscosity, that it would
be entirely possible to treat the subject of viscosity by consider-
ing in turn these dominant ideas.
Practically no measurements from which viscosities may be
calculated were made prior to 1842, yet very important work
was being done in Hydrodynamics, and the fundamental laws
of motion were established during this preliminary period. To
this group of investigations belong the classical researches of
Bernouilli (1726), Euler (1756), Prony (1804), Navier (1823),
and Poisson (1831). In the development of Hydrodynamics
much experimental work was done upon the flow of water in
pipes of large bore by Couplet (1732), Bossut (1775), Dubuat
(1786), Gerstner (1800), Girard (1813), Darcy (1858), but this
work could not lead to the elucidation of the theory of viscosity
as we shall see. Important work belonging to this preliminary
period was also done by Mariotte (1700), Galileo (1817), S'Grave-
sande (1719), Newton (1729), D'Alembert (1770), Boscovich
(1785), Coulomb (1801), Eytelwein, (1814).
It is to Poiseuille (1842) that we owe our knowledge of the
simple nature of flow in capillary spaces, which is in contrast
with the complex condition of flow in wide tubes, heretofore
used. He wished to understand the nature of the flow of the
blood in the capillaries, being interested in internal friction from
the physiological point of view. He made a great many meas-
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