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III. On the expediency of assigning specific names to all such 
functions of simple elements as represent definite physical pro- 
perties ; with the suggestion of a new term in mechanics ; 
illustrated by an investigation of the machine moved by recoil , 
and also by some observations on the Steam Engine . By Davies 
Gilbert, Esq. M. P. V. P. R. S. &c. 
Read January 25, 1827. 
The expediency of distinguishing by separate appellations, 
all such functions of simple elements as measure the intensity 
of physical properties, will be rendered obvious by referring 
to the well known controversy respecting motion. 
Scarcely had the principles which regulate the action of 
bodies in motion become subjected to mathematical calcula- 
tion, when a dispute arose as to the measure of motion itself ; 
a dispute conducted with much more vehemence and acri- 
mony than might be supposed incident to the nature of an 
abstract subject. 
Several individuals of the greatest learning and reputation 
contended that weight, multiplied by velocity, (ze x v) gave 
a product always proportionate to the motion of bodies, as 
was proved by a comparison of their inertias, by all the 
properties relative to the common centre of gravity in pla- 
netary systems, &c. &c. &c. ; while other persons, scarcely 
inferior to the former, adverting to the collision of elastic 
bodies, and to the extremely curious property of motion, the 
conservatio virium vivarum, contended with equal confidence, 
that the true measure of motion was weight multiplied into 
MDCCCXXVII. E 
