VI.] 



THE INDIRECT METHOD OF INFERENCE. 



109 



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 argu- 

 ment 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 

 cond)inations 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 condjination 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 — 



