C 2 5 + ] 
and then recede from it without paffing under it, 
twice fo many will be the number of impoffible 
roots in that equation. N. B. There are fome fmall 
pieces fcrewed on to the perpendicular pillars E F, 
G H, I K and L M, three of which appear at 21, 
22, and 23 ; thefe ferve only to prevent the bars 
which Aide under them from rifing up. 
To re&ify the machine for a propofed equation. 
Screw the nuts e and /, which carry the 
filken cord at any equal diftances from the pillars 
E F and L M. Then Aide the nut c, which carries 
the extremity of the bar a b t till it is farther from 
the pillar EF than the place you have fixed the nut 
e at, by a number of divifions upon any fcale of equal 
parts, equal to the known term of the equation, if 
that term be affirmative ; but fo much nearer to it, 
if that term be negative ; and fix it there. Then 
Aide the nut N that carries the bar N O, till it is 
farther from or nearer to the pillar E F, than the 
laft nut c is, by a number of divifions taken from 
the fame feale, equal to the fecond coefficient of the 
equation (I mean that, where the unknown quantity 
is of one dimenfion)j farther from it, if that coeffi- 
cient is affirmative j but nearer, if it is negative : and 
fix it there. Then, laftly, Aide the nut R, which 
fixes the other end of the bar N O,. till it is farther 
from a line drawn from the pillar EF to LM, that 
is, farther from the fide D of the frame than the 
laft nut N is from the fame, as many divifions, as the 
coefficient of that term of the equation, where the 
unknown quantity is of two dimenfions,. indicates ; far- 
ther.,. 
