Review of O. Gregory’s Treatise ow Mechanics. 
al to the components.” This proposition, though taken 
from Francceur, and repeated by other French writers 
venture to oppugn, as mathematically and physically in- 
correct. 
‘A force aeting perpendicularly on a mere mathematical 
line, it is evident, can communicate no force to it, either 
longitudinally, or laterally, except at the very point where 
it acts: for the action, in such case, in the direction of 
the line is nothing by the principles of mechanics, and no 
other part of the line, admitting it to be cohesive, can be 
affected by'a force at a distance from it, unless there be 
some longitudinal action ; this can take place only when 
the line is riot perpendicular to the direction of the force 
acting on it, or when it is oblique to that direction 3 but it 
di- 
rection. Without the consideration of an oblique force, it 
appears to us impossible to solve this problem, as its cons 
ditions are evidently impossible. . ME wor 
Bat supposing the line to be a physical quantity, or m 
the practical sense, to have length, breadth, and_thick- 
hess, each of which is of some definite quantity, in this 
Case, it is no longer a line, but a material. b Y, possessing 
the properties and dimensions of a solid. . If this. material 
substance be of sufficient cohesive strength, parallel forces, 
acting in the manner of the proposition on its ‘surface, will 
Produce a lateral action, together witha lon itudinal ac- 
tion, which, though the forces be unequal, at different dis- 
tances, may counterbalance each other. . But it shouid be. 
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