80 G. H, KNIBBS. 
interval Navier' published his celebrated memoir in which the 
theory of the motion of a viscous fluid is mathematically treated 
The memoir was read in January 1817 at the French Academy 
of Sciences. Shortly before 1835 the attention of Poiseuille? was 
strongly directed to the subject of venous and arterial flow, to 
establish the laws of which on a rational basis,’ he undertook, 
about 1838, a lengthy investigation of flow in capillary tubes 
This enabled him to correctly enunciate the law of flow for such 
tubes, and to furnish an expression for the efflux therefrom 
between the temperature limits 0° and 45° centigrade. His 
experiments remain, I venture to think, unrivalled even to-day, % 
regards their general precision. Girard’s formula previously 
mentioned, and Navier’s intrinsically identical therewith, bub 
theoretically established, were shown to be inapplicable in regard 
to efflux from capillaries. These researches were published in 
great detail in 1846, in the Mémoires des savants étrangers, and, 
as we shall see later on, supply material for determining the 
viscosity with a high degree of precision, and for testing the 
validity of and evaluating the constants of necessary corrections 
to be applied to the immediate data of any observation. Poiseuille 
himself did not, however, deduce the viscosity coéficient, not 
recognize the necessity for the corrections, and his enunciation of 
the law, though accurate, left the matter in the empirical stage- 
Before the above mentioned publication tolerably complete 
information had already appeared from time to time in the 
‘Comptes rendus’ as to the scope and results of these researches 
and in April 1845, that is before the detailed results had appeared) 
Stokes,* in his contribution to the mathematical theory of internal 
iyi i 
eo Mémoire sur les lois du errant des fluides.—Mém. de ro 
Sane Coe 440, 1 
2 Recherches e Rabe sur _ mouv 
ement des a 
tubes de trba.petit diiecae —Mem. des Sav. étrang. t. 9, P 
% Physiologists and pathologists had A * tame 
ous movement to blood mits iach apiegreny the power 0 a 
n the theories of the internal friction of fluids in motion and of ti 
equilicinen and motion of elastic solids,— Cambridg® 
Vol. 8, p. 287 - 319, 1849. Denon tl Bers 
