Part IV.] 
PRUNING AND THINNING. 
243 
of reach, a string may sometimes be swung over 
one of its boughs by a weight, or shot over with 
a blunt arrow, and by this a rope hauled over. 
Seated in a loop at one end of the rope, or with 
one end tied round the thigh, the hands on the 
opposite rope will acquire the mechanical advan¬ 
tage of a fixed and movable pulley; that is, 
the double rope doubles your power, or, in this 
case I should say, halves your exertion, and 
you may raise your whole weight with half the 
exertion required without a pulley. Let us call 
this natural pulley, the pruner’s pulley. It is 
often useful to reach the head, or to remove 
dead wood or a detached branch on an otherwise 
branchless stem, or to make the pruner safe; 
and would make a good fire-escape. 
In explanation I attach an engraving from 
Chambers’s excellent educational 
course, “ Mechanics,” 1837. The 
writer, however, like others, has 
entirely mistaken the principle of 
this curious mechanical paradox. 
In mechanics, indeed, no axiom 
is more certain than that without 
two pulleys, that is, with the fixed 
‘pulley only, and without the mov¬ 
able pulley also, no mechanical advantage is 
R 2 
