we press the keys A (left), copula, A (right), B (right), and full stop.
If there be a second premise, for instance
B = BC,
we press in like manner the keys—
B (left), copula, B (right), C (right), full stop.
The process is exactly the same however numerous the premises may be. When they are completed the operator will see indicated on the face of the machine the exact combinations of letters which are consistent with the premises according to the principles of thought.
As shown in the figure opposite the title-page, the machine exhibits in front a Logical Alphabet of sixteen combinations, exactly like that of the Abacus, except that the letters of each combination are separated by a certain interval. After the above problem has been worked upon the machine the Logical Alphabet will have been modified so as to present the following appearance—
| A | A |
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| a | a |
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| a | a | a | a |
| B | B | B | B | b | b | b | b | ||||||||
| C | C | C | C | C | C | c | c | ||||||||
| D | d | D | d | D | d | D | d | ||||||||
The operator will readily collect the various conclusions in the manner described in previous pages, as, for instance that A is always C, that not-C is not-B and not-A; and not-B is not-A but either C or not-C. The results are thus to be read off exactly as in the case of the Logical Slate, or the Logical Abacus.
Disjunctive propositions are to be treated in an exactly similar manner. Thus, to work the premises