132 Remarks on Drv ee 
i 1 arn 
: uy theory o of e ilib: i Wwers (chap. 
vi,) might have been stated i ina more concise and popular 
f virtual velocities, to make 
room for a biel account of) prime movers, and the motion 
and maximum effect machines. The subjects os frietion, 
and the construction eel carriages, are now 
iv half. a page,—less ine half the room seekinielk by the 
and almost useless Se noes onthe wedge. ‘These 
and practi 
in detail ; nor ought the fc rounded on the 
‘iments of Vince, to the wx blaidets ae ‘the much: more 
important ge diversified ones of Coulomb. In chapter vir. 
the mathematical theory of projectiles is pursued to the. 
length of ten or twelve propositions ; and we-are left to an 
incidental remark of a single sentence inserted by the editor 
of the second edition, for all our information concerning the 
total discrepancy between theory” and practice. Several 
parts of vei chveipiee possess very little interest, even in a 
mathematica t of view ; and had they been much more 
important than they are, they: ought to have given way to 
such a statement of the principal results of experiment on 
the motion of projectiles as the writings of Robins, Rum- 
‘ford, and Hutton mighthave easily furnished. | Several lem- 
mas introduced from the Principia, into the concluding see- 
tion on central forces, although needed forthe objects which 
the original author had in view, are here entirely out of 
place. Such of them as were wanted should have been di- 
vested of their latinized idiom, and translated into a more- 
modern and aitelligible: dialect. Several oe the more im- 
portant theorems relating to motion by a central force vary- 
ing inversely as the square of the distance, pre have been 
subjoined with the utmost advantage to the single one with 
which the Book now eloses.—The subjects of rotatory mo- 
tion, the funicular Polygon and =. of arches, the 
ofthe distance dooms the} west point, 0 or ultimate! y asthe distance itself. This 
J j of , hat l 
times of ee in the are ; and chord approach to an ultimate ratio- 
‘toa ratio of finite inequality. No one but the stu- 
eee informed that the former is ha ee the ratio of 
