My mind got a start by and by, and began to consider the beginning of every subject which has ever been thought of; but it never went further than the beginning; it was touch and go; it fled from topic to topic with a frantic speed.

At the end of an hour my head was in a perfect whirl and I was dead tired, fagged out.
The fatigue was so great that it presently began to make some head against the nervous excitement; while imagining myself wide awake, I would really doze into momentary unconsciousness, and come suddenly out of it with a physical jerk which nearly wrenched my joints apart--the delusion of the instant being that I was tumbling backward over a precipice.

After I had fallen over eight or nine precipices and thus found out that one half of my brain had been asleep eight or nine times without the wide-awake, hard-working other half suspecting it, the periodical unconsciousnesses began to extend their spell gradually over more of my brain-territory, and at last I sank into a drowse which grew deeper and deeper and was doubtless just on the very point of being a solid, blessed dreamless stupor, when--what was that?
My dulled faculties dragged themselves partly back to life and took a receptive attitude.

Now out of an immense, a limitless distance, came a something which grew and grew, and approached, and presently was recognizable as a sound--it had rather seemed to be a feeling, before.
This sound was a mile away, now--perhaps it was the murmur of a storm; and now it was nearer--not a quarter of a mile away; was it the muffled rasping and grinding of distant machinery?
No, it came still nearer; was it the measured tramp of a marching troop?
But it came nearer still, and still nearer--and at last it was right in the room: it was merely a mouse gnawing the woodwork.

So I had held my breath all that time for such a trifle.
Well, what was done could not be helped; I would go to sleep at once and make up the lost time.