( 9 ° ) 
catch (as in G, Fig. 5 ) which may be eafily felr. 
Obferve in the Silver Plate, where thelndex w points^ 
and there engrave the Number or Figure 9, lower 
down in the Subflraflion- Ring, where the Index/ 
points, engrave the Cypher 0. After this divide 
both Rings into 10 equal Parts, one of which 
is already defigned for 9 in the Addition , and ano- 
ther for 0 in the Snbftra£lion-Ring 3 then obferve 
which way the Wheel turns, if from the right to 
the left, as in Syflem BB ; then you muft from the 
engraved Number 9 in th ^ Addition- Ring^ towards 
the right engrave 0 nexr, then 1,2, 3,4, &c. and in 
the Suhjlrabt ion- Ring towards the right alfo, from 
the already engraved 0, firfl engrave 9, then 8, 7, 6, &c. 
or dine inverjo . But if the Wheel turns from the left 
to the right, as in the Syftems AA and CC, you en- 
grave the Numbers or Figures in the fame Order, 
but from the right to the left (See in Fig. 1. the 
Syjlems BB and CC.) 
In the Multiplication-Wheels mm you mull: con- 
duct the Index ff exactly to the Window, as it is 
drawn in the Syflem BB ; mark thePlace on the round 
Multiplication-T late under the Window, and en- 
grave upon it the Cypher or 0 : Then make, by two 
concentrick Circles, a Ring upon this Plate, and di- 
vide this Ring into ten equal Parts, and after the 0 
(already engraved) engrave on the Numbers 1, 2, 3, 
4? 5-> 63 7> 8, 9> in the fame Order as it was done 
in the Addition-Ring of the Silver-Plate of the fame 
Syflem. Laft of all, if you think fit, you may skrew 
on thin Ivory Plates, to note upon them the Num- 
bers which are to be calculated, particularly a long 
fmall one on that Side of the Slit of the Determi- 
nator, where there are no Numbers, and alfo two 
fhorter 
