C 1 r 9 ] 
The proportion, which any power bears to the re- 
fitting force it is able to fuftain by means of a wedge, 
has been laid down differently by different authors ; 
fome of whom therefore mutt have been mittaken : 
and none of them feem to have treated the matter fo 
generally as they might have done. Without exa- 
mining their feveral opinions, I (hall proceed to con- 
fider what proportion a power ading on a wedge 
muff have to the remittance it fuftains in three different 
cafes, to whicji I think all thofe relating to the wedge 
may be reduced. 
Firjl , When the refitting bodies ad perpendicularly 
on the fides of the wedge, and recede alfo in lines per- 
pendicular to the fides. 
Secondly, When the refitting bodies ad on the wedge 
in oblique directions equally inclined to the fides, and 
recede in lines perpendicular to the fides. 
Thirdly, When the refitting bodies are confined, by 
planes put under them, or otherwife, to recede in 
particular directions oblique to the fides. 
CASE I. 
Let the aequicrural triangle A, B, C, [Tab. VI. Fig, 
3,] reprefent a wedge on whofe fides the two equal 
refitting forces E and F aCt perpendicularly with lines 
of direction meeting at the point D, at which the 
power P ads perpendicularly on the bafe A C. Then, 
fince thefe three forces are fuppofed to 'fuftain each 
other and keep the wedge in asquilibrio, they mutt be 
to each other as the fides of a triangle to which their 
directions are parallel, and therefore they will be to 
each other as the fides of a triangle to which their 
diredions 
