III. Next, after the most vigorous attention, and a scientific attention to the digestive system, in power of operation, stands _exercise_. Here, however, most people have their own separate habits, with respect to the time of exercise, the duration, and the particular mode, on which a stranger cannot venture to intrude with his advice. Some will not endure the steady patience required for walking exercise; many benefit most by riding on horseback; and in days when roads were more rugged, and the springs of carriages less improved, I have known people who found most advantage in the vibrations communicated to the frame by a heavy rumbling carriage. For myself, under the ravages of opium, I have found walking the most beneficial exercise; besides that, it requires no previous notice or preparation of any kind; and this is a capital advantage in a state of drooping energies, or of impatient and unresting agitation. I may mention, as possibly an accident of my individual temperament, but possibly, also, no accident at all, that the relief obtained by walking was always most sensibly brought home to my consciousness, when some part of it (at least a mile and a half) has been performed before breakfast. In this there soon ceased to be any difficulty; for, whilst under the full oppression of opium, it was impossible for me to rise at any hour that could, by the most indulgent courtesy, be described as within the pale of morning, no sooner had there been established any considerable relief from this oppression, than the tendency was in the opposite direction; the difficulty became continually greater of sleeping even to a reasonable hour. Having once accomplished the feat of walking at nine A. M., I backed, in a space of seven or eight months, to eight o'clock, to seven, to six, five, four, three; until at this point a metaphysical fear fell upon me that I was actually backing into 'yesterday,' and should soon have no sleep at all. Below three, however, I did not descend; and, for a couple of years, three and a half hours' sleep was all that I could obtain in the twenty-four hours. From this no particular suffering arose, except the nervous impatience of lying in bed for one moment after awaking. Consequently, the habit of walking before breakfast became at length troublesome no longer as a most odious duty, but, on the contrary, as a temptation that could hardly be resisted on the wettest mornings. As to the quantity of the exercise, I found that six miles a day formed the _minimum_ which would support permanently a particular standard of animal spirits, evidenced to myself by certain apparent symptoms. I averaged about nine and a half miles a day; but ascended on particular days to fifteen or sixteen, and more rarely to twenty-three or twenty-four; a quantity which did not produce fatigue, on the contrary it spread a sense of improvement through almost the whole week that followed; but usually,