( 9 * ) 
the great or uppermoft Wheel a to flide alfo over 
two Teeth ; at the fame time the Tooth of Com- 
munication $ will move forward one Tooth of the 
uppermoft Ratchet-Wheel in the Syftem CC ; con- 
fequently on the Silver-Plate in B B, inftead of 9 
the Number 1, and in Syftem C C, inftead of 5- the 
Number 6 muft appear under their Indexes ww; 
and fo for the fame leafon, having pulled up and 
down the Operator of the Syftem C C, the Number 
6 pointed to by the Index muft be at laft changed 
into 9. 
II. Subjiratlion . Suppofe 40 the Sum, from 
which you are to fubftrad xq : Here you muft put 
your Sum 40 in the Subjlratt ion- Rings , that is to 
fay, turn the Cypher 0 in the Syftem B B, and the 
Number 4 in the Syftem C C, under the Indexes 
as the Figure fliews : Set the Determinators at 24, 
as in Addition ; move alfo the Operators only once 
up and down, the Remainder 16 will appear under 
the Indexes yy. As for the Reafon of this Opera- 
tion, when you confider, that the Numbers in the 
Subjiraffion-Rings are engraved inverfo ordinc , as 
it is faid before, you will find that it is the fame as 
in Addition. 
III. Multiplication. For inftance 5 if you are 
to multiply 43 by 3, bring the 0 in all your Addi- 
tiourRings to the Indexes, as aho in all your MuU 
tiplication-Tlates in the Windows. Write down 
(which is more particularly necefiary if the Num- 
bers are larger than here) the Multiplicand 43 upon 
the Ivory- Plates near the two Determinators in the 
two Sy items B B and C C : But the Multiplicator 3, 
you may write only on the Ivory-Plate under the 
Window 
