any difficulty; for, while 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 9 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, in the night immediately succeeding to such an exertion, I lost much of my sleep--a privation that under the circumstances explained, deterred me from trying the experiment too often. For one or two years I accomplished more than I have here claimed, viz., from six to seven thousand miles in the twelve months.