312 On Printing Presses and their Theory. 
summer, where the spindle was inserted, was attached a 
species of inclined plane, rounded off so as to have a varia- 
ble inclination. ‘Through the spindle immediately beneath 
ran a cross bar, which plied against this winding surface, 
and forced the spindle down as it was turned round; rapidly 
at first, but more.slowly as the inclination diminished, and 
at last with a velocity as trifling as was shewn by experi- 
ence to put the press into the best working state. In a 
press recently invented by Mr. Medhurst, an ingenious Eng- 
lishman, the power is gained by means of two iron rods, 
one on each side of the spindle. These rods pass down 
from the summer to the top surface rl a circular beta 
ment of the spindle, and rest at each end in hollows which 
allow them a racking motion. The Sind extremities of each 
are tags from the centre of the spindle, but are pla- 
nding position when the platen is raised. The 
bier turns c spindle partly round, and moves the lower 
ends. of notes rods so that they come — a vertical posi- 
tion, and bear down the platen with t ind of ances 
hanical power which every one has eee exemplified in 
bes ging a prop erect by driving at right angles against the 
ottom. 
But in most of the recent attempts to improve the con- 
struction of the printing press, a kind of mechanical power 
has been resorted to in different forms, somewhat different 
from either of the foregoing; one which is well known to 
every theoretical and practical mechanician, but which has 
scarcely acquired a distinct name. To attempt to reduce it 
to the head of the lever or wedge, as has been sometimes 
done, appears an unwarrantable extension of the meaning 
of ntieba terms; and yet I know not how to designate the 
Aaeat ds better than to call s oe of combined levers. At is 
The pail of this combination will ae ove in 1 the Sorte 
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