ARISTOTELIAN MECHANICS 
345 
namely that the line which is farther from the centre describes 
the greater circle, so that, if the power applied is the same, 
that which moves (the system) will change its position the 
more, the farther it is away from the fulcrum.’ 1 
The idea then is that the greater power exerted by the 
weight at the greater distance corresponds to its greater 
velocity. Compare with this the passage in the De caelo 
where Aristotle is speaking of the speeds of the circles of 
the stars: 
* it is not at all strange, nay it is inevitable, that the speeds of 
circles should be in the proportion of their sizes.’ 2 ‘ Since 
in two. concentric circles the segment (sector) of the outer cut 
off between two radii common to both circles is greater than 
that cut off on the inner, it is reasonable that the greater circle 
should be carried round in the same time.’ 3 
Compare again the passage of the Mechanica: 
1 what happens with the balance is reduced to (the case of the) 
circle, the case of the lever to that of the balance, and 
practically everything concerning mechanical movements to 
the case of the lever. Further it is the fact that, given 
a radius of a circle, no two points of it move at the same 
speed (as the radius itself revolves), but the point more distant 
from the centre always moves more quickly, and this is the 
reason of many remarkable facts about the movements of 
circles which will appear in the sequel.’ 4 
The axiom which is regarded as containing the germ of the 
principle of virtual velocities is enunciated, in slightly different 
forms, in the De caelo and the Physics : 
‘ A smaller and lighter weight will be given more movement 
if the force acting on it is the same. . . . The speed of the 
lesser body will be to that of the greater as tire greater body 
is to the lesser.’ 5 
‘If A be the movent, B the thing moved, C the length 
through which it is moved, D the time taken, then 
A will move hB over the distance 2 C in the time D 
and A „ %B 
thus proportion is maintained.’ G 
1 Mechanica, 8, 850 b 1. 
3 Ih. 290 a 2. 
5 De caelo, iii. 2. 301 b 4, 1L 
C i /)• 
^ 5! 5) 2 1 3 
2 De caelo, ii. 8. 289 b 15. 
4 Mechanica, 848 a 11. 
6 Phys. vii. 5. 249 b 30-250 a 4.