A. DE MORGAN.

UNIVERSITY COLLEGE, LONDON,

_April 29, 1847_.

⁂ In consequence of a little change in the plan of this work, made

after the printing was commenced, there may be one or two places in

which the reader must consult the _Introduction_, where he is told to

consult the _Index_; and the _Additions_, where he is told to consult

the _Introduction_.

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