9 
Austin, in his ^'Lectures on Jurisprudence” (voL ii, p. 865) 
says it is used by the Roman lawyers. But there is much 
that is interesting in the other investigations on the subject. 
10. Lagrange {ih. p. 29) uses the term ‘"moment” in the 
sense which Galileo {ih. p. 20) gave it, viz : the product of 
the force into its virtual velocity ; noticing however another 
{ih. p. 7) meaning viz. the product of the force into the arm 
of the lever by which it acts. 
11. Whewell (Hist. Ind. Sci., i, 93), speaking of a “matter 
of obvious and universal experience,” says 
“ This general fact is obvious, when we possess in our minds the 
ideas which are requisite to apprehend it clearly. When we are 
so prepared, the truth appears to be manifest, independent of 
experience, and is seen to be a rule to which experience must 
conform.” 
He seems {ih. ii, 25) to reiterate this opinion, which, if 
“appears to be manifest” be taken to mean “is self-evident,” 
will hardly pass unquestioned. 
12. Lagrange ("Mec. An.’ i, 4, 5) tells us, in words which I 
translate as follows, to 
“ imagine a triangular plane loaded with two equal weights at 
the tw^o ends of its base, and with a double weight at its vertex. 
This plane will evidently be in equilibrium, w^hen supported by a 
straight line or fixed axis, which passes through the middle of the 
two sides of the triangle j for we may regard each of these sides as 
a lever loaded at its two ends with two equal weights, and w^hich 
has its fulcrum on the axis which passes through its middle. 
Now w’e may contemplate this equilibrium in another manner, by 
regarding the base itself of the triangle as a lever of which the 
ends are loaded with two equal weights ; and by imagining that 
there is a transverse lever which joins the vertex of the triangle 
and the middle of its base in the form of a T, and of which one 
end is loaded with the double weight placed at the vertex, and 
the other serves as the fulcrum of the lever which forms the base. 
Tt is evident that this last lever will be in equilibrium on the 
transverse lever which sustains it at its middle, and that the 
transverse lever will consequently be in equilibrium on the axis 
