( «» ) 
too intricate^ nor that the working of it took up 
too much time. 
But at prefent, being certain that none ol 
Mr. Leibnitz's Invention has yet appeared in fuch 
a State of Perfection, as to have anfwer’d the Effect 
propofed, and that thefe of mine differ from all thole 
mentioned above, fancying at the fame time, that 
Perfons who underftand Mechanicks, will find it 
plain, practicable, and exact, in regard to its various 
Effects, I make no Scruple to prefent to the Royal 
Society this Invention, the Produt of my younger 
Years indeed, but now with the feveral Amend- 
ments 1 have fince added to it, as a Mark of the 
Refpect and Veneration 1 have for this illuftrious 
Body. 
The Particulars of it are as follows : 
There are as many Sets of Wheels and moveable 
Rulers as there are Places in the Numbers to be cal- 
culated. Fig. i. lhews three of them, by which 
one may eafily conceive the reft. A A lhews the 
firft Syftem or the Figures of Unites, according to 
its inward Stru&uie. B B and C C fhews the fecond 
and third Syftem, viz. of Tens and Hundreds, ac- 
cording to their outward Form. We lhall firft con- 
fider A A ; where ccaoc is a flat Bottom of a Brafs 
Plate, which may be skrewed on either upon a par- 
ticular Iron Frame, or only upon a ftrong Piece of 
Walnut-Tree, doubled with the Grain crofs’d. In 
this Syftem are two moveable Rules gggg, and kkk , 
the firft of which I call the Operator, the fecond 
the Determinator. There are befides two Wheel- 
Works, the upper one is for Addition and Sub - 
Jlra£lion } the lower one lerves for Multiplication 
