Lines for the purpofe of Computation . 2 5 1 
line CD or Eh is to be placed at the confequent, and the line in 
the piece AB at the antecedent : then, if the piece AB be placed at 
any other antecedent, the fame line CD or EF will indicate its 
confequent in the fame ratio taken the fame way; that is to 
fay, if the antecedent and the confequent lie on the fame fide 
of the Aider, all other antecedents and confequents in that 
ratio will lie in the fame manner; and the contrary if they 
do not, &c. But if the confequent line fill without the rule, 
the other fixed line on the Aider will fhew the confequent ; 
but on the contrary fide of the Aider to that where it would 
elfe have been feen by means of the firA confequent line. 
Fig. 4. is an inArument equivalent to the fame rule of 28 f 
inches long. It confifts of three concentric circles engraved 
and graduated on a plate of about 1 \ inch in diameter. From 
the center proceed two legs A, B, having right-lined edges in 
the direction of radii. They are moveable either fingiy or 
together. To ufe this inArument, place one of the edges at 
the antecedent, and the other at the confequent, and fix them 
to that angle. The two legs being then moved together, and the 
antecedent leg placed at any other number, the other leg will 
give its confequent in the like pofition or fituation on the lines. 
If the line CD happen to lie between the legs, and B be the 
confequent leg, the number fought will be found one line far- 
ther from the center than it would otherwife have been ; and, 
on the contrary, it will be found one line nearer in the like 
cafe, if A be the confequent leg. This inArument, differing 
from fig. 1. only in its circular form, and the advantages re- 
fulting from that form, the lines- muA be taken to fucceed each 
other in the fame manner laterally; fo that numbers, which 
fall either without or within the arrangement of circles, will 
4 be 
