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generality of a new system of pure Qualitative Logic closely 
analagous to, and suggested by, the mathematical system of 
logic of the late Professor Boole, hut strongly distinguished 
from the latter by the rejection of all considerations of 
quantity. 
This logical abacus leads naturally to the construction 
of a simple machine which shall be capable of giving 
with absolute certainty all possible -logical conclusions from 
any sets of propositions or premises read off upon the keys 
of the instrument. The possibility of such a contrivance is 
practically ascertained; when completed it will furnish a 
more signal proof of the truth of the system of logic embodied 
in it. Still the more rudimentary contrivance called the 
abacus will remain the most convenient for explaining the 
nature and working of formal inference, and may be usefully 
employed in the lecture room, for exhibiting the complete 
analysis of arguments and logical conditions, and the expo- 
sure of fallacies. 
The abacus consists of — 
1. An inclined black board, furnished with four ledges, 
3ft. long, placed 9in. apart. 
2. Series of flat slips of wood, the smallest set four in 
number, and other sets, 8, 16, and 82 in number, marked 
with combinations of letters, as follows : — 
First Set. 
A 
A 
a 
a 
B 
b 
B 
b 
Second Set. 
a 
b 
C 
The third and fourth sets exhibit the corresponding com- 
binations of the letters A, B, C, 1), a, b, c, d } and A, B, C, 
U, E, a, b, c, d, e. 
