_Mental Action modified by certain Causes in Sleep._--The faculties will, however, be materially modified in their action during sleep, by the causes already named; chiefly these two: 1st. the entire suspension of voluntary control over the train of thought; 2d. the loss of personal consciousness as regards especially the bodily organization, and its present relations to time, and space, and all sensible objects. In consequence of the _former_ our thoughts will come and go all unregulated and disconnected; there will be no coherence; the slightest analysis will suffice for the associating principle; we shall be hurried on and borne away on the rushing tide of thought, as a frail passive leaf swept on the bosom of the rapids; we shall whirl hither and thither as in the dance of the witches; we shall waken in confusion, and seek to recover the reins of self-control, only to lose them again and be swept on in the fearful dance. _Want of Congruity owing to what._--In consequence of the _latter_ cause--the loss of sensational consciousness and of our relations to sensible objects--there will be an entire want of fitness and congruity in our mental operations. The laws of time, and space, and personal identity, will be altogether disregarded, and we shall not be conscious of the incongruity, nor wonder at the strangest and most contradictory combinations. Here, there, everywhere, now this and now that. The scene is in the valley of the Connecticut, and anon on the Ural mountains, or the desert of Arabia, and we do not notice the change as any thing at all remarkable. Now we are walking up the aisle of the church, in garments all too scanty for the proprieties of the occasion, and now it is a wild bull that is racing after us, and the transition from one to the other is instantaneous. Why should it not be, for it is by the senses alone that we are brought into conscious relation to the external world, and so made cognizant of the laws of time and space, and those senses being now locked in oblivion, what are time and space to us? _The Causes now named a sufficient Explanation of the Phenomena._--The causes already named will sufficiently account for the strange and distorted action of the various mental faculties as exercised in sleep. Memory, _e. g._, will give us the past with _variations_ ad libitum; things will appear to us, and events will seem to transpire, and forms and faces familiar will look out upon us, not as they really are, or ever were. We talk with a former friend, without the thought once occurring to us that he has been dead these many years. Impression there is, feeling, idea, fancy, association of all these, but hardly memory, or even imagination, much less judgment or reasoning. So it would seem at first. A closer inspection, however, will show us that there is in reality, in this spontaneous play of the mind, the exercise of all these faculties, only so modified by causes now named as to present strange and uncouth results.