upon a frame of moderate strength would, perhaps, make the man
kill himself by his exertions, but it would not make him walk a hundred
miles in twenty-four hours. This statement of the case shews the
fallacy of supposing that the person was really not at all tired in his
first walk of twenty miles, because he did not appear to be so, or,
perhaps, scarcely felt any fatigue himself. The mind cannot fix its
attention strongly on more than one object at once. The twenty thousand
pounds so engrossed his thoughts that he did not attend to any slight
soreness of foot, or stiffness of limb. But had he been really as fresh
and as alert, as when he first set off, he would be able to go the
second twenty miles with as much ease as the first, and so on, the
third, &c. Which leads to a palpable absurdity. When a horse of spirit
is nearly half tired, by the stimulus of the spur, added to the proper
management of the bit, he may be put so much upon his mettle, that he
would appear to a standerby, as fresh and as high spirited as if he had
not gone a mile. Nay, probably, the horse himself, while in the heat
and passion occasioned by this stimulus, would not feel any fatigue;
but it would be strangely contrary to all reason and experience, to
argue from such an appearance that, if the stimulus were continued, the
horse would never be tired. The cry of a pack of hounds will make some
horses, after a journey of forty miles on the road, appear as fresh,
and as lively, as when they first set out. Were they then to be hunted,
no perceptible abatement would at first be felt by their riders in
their strength and spirits, but towards the end of a hard day, the
previous fatigue would have its full weight and effect, and make them
tire sooner. When I have taken a long walk with my gun, and met with no
success, I have frequently returned home feeling a considerable degree
of uncomfortableness from fatigue. Another day, perhaps, going over
nearly the same extent of ground with a good deal of sport, I have come
home fresh, and alert. The difference in the sensation of fatigue upon
coming in, on the different days, may have been very striking, but on
the following mornings I have found no such difference. I have not
perceived that I was less stiff in my limbs, or less footsore, on the
morning after the day of the sport, than on the other morning.

In all these cases, stimulants upon the mind seem to act rather by
taking off the attention from the bod