+-+-----------------------------------+-+-----------------------------------+---+ | | |C| | | |F| Left-hand side of Proposition. |o| Right-hand side of Proposition. |F S| |i| |p| |u t| |n+---+---+---+---+---+---+---+---+---+u+---+---+---+---+---+---+---+---+---+l o| |i| | | | | | | | | |l| | | | | | | | | |l p| |s|ꖌ|*d*| D |*c*| C |*b*| B |*a*| A |a| A |*a*| B |*b*| C |*c*| D |*d*|ꖌ| .| |.|Or | | | | | | | | |.| | | | | | | | | Or| | +-+---+---+---+---+---+---+---+---+---+-+---+---+---+---+---+---+---+---+---+---+ To work the machine it is only requisite to press the keys in succession as indicated by the letters and signs of a symbolical proposition. All the premises of an argument are supposed to be reduced to the simple notation which has been employed in the previous pages. Taking then such a simple proposition as A = AB, 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--