same posture, and his whole soul apparently wrapped in
the purpose of placing his foot exactly on the same spot of each step
which had been occupied by the officer who preceded him. At the door
of the hall the porter again drew off, saluted with his staff, and
bowed reverentially. The philosopher again imitated his motions, and
returned his bow with the most profound gravity. When the Doctor
entered the apartment the spell under which he seemed to act was
entirely broken, and our informant, who, very much amused, had
followed him the whole way, had some difficulty to convince him that
he had been doing anything extraordinary."[287]

This inability to recollect in a completely waking state what had
taken place during the morbid one separates this story from all the
rest that are told of Smith's absence of mind. For his friends used
always to observe of his fits of abstraction what a remarkable faculty
he possessed of recovering, when he came to himself, long portions of
the conversation that had been going on around him while his mind was
absent. But here there is an entire break between the one state and
the other; the case seems more allied to trance, though it doubtless
had the same origin as the more ordinary fits of absence, and, like
them, was only one of the penalties of that power of profound and
prolonged concentration to which the world owes so much; it was
thinker's cramp, if I may use the expression. In one way Smith took
more interest in his official work than ordinary Commissioners would
do, because he found it useful to his economic studies. In 1778 he
wrote Sir John Sinclair, who had desired a loan of the French inquiry
entitled _Memoires concernant les Impositions_, that "he had frequent
occasion to consult the book himself both in the course of his private
studies and in the business of his present employment," and Sir John
states that Smith used to admit "that he derived great advantage from
the practical information he derived by means of his official
situation, and that he would not have otherwise known or believed how
essential practical knowledge was to the thorough understanding of
political subjects."[288] This is confirmed by the fact that most of
the additions and corrections introduced into the third edition of the
_Wealth of Nations_--the first published after his settlement in the
Customs--are connected with that branch of the public service.

Still his friends were perhaps right in lament