So those who are accustomed at intervals to cross the Atlantic, get into certain habits on board ship, different to their usual ones. It may be that at home they never play whist; on board ship they do nothing else all the evening. At home they never touch spirits; on the voyage they regularly take a glass of something before they go to bed. They do not smoke at home; here they are smoking all day. Once the voyage is at an end, they return without an effort to their usual habits, and do not feel any wish for cards, spirits, or tobacco. They do not remember yesterday, when they did want all these things; at least, not with such force as to be influenced by it in their desires and actions; their true memory—the memory which makes them want, and do, reverts to the last occasion on which they were in circumstances like their present; they therefore want now what they wanted then, and nothing more; but when the time comes for them to go on shipboard again, no sooner do they smell the smell of the ship, than their real memory reverts to the times when they were last at sea, and striking a balance of their recollections, they smoke, play cards, and drink whisky and water. We observe it then as a matter of the commonest daily occurrence within our own experience, that memory does fade completely away, and recur with the recurrence of surroundings like those which made any particular impression in the first instance. We observe that there is hardly any limit to the completeness and the length of time during which our memory may remain in abeyance. A smell may remind an old man of eighty of some incident of his childhood, forgotten for nearly as many years as he has lived. In other words, we observe that when an impression has been repeatedly made in a certain sequence on any living organism—that impression not having been prejudicial to the creature itself—the organism will have a tendency, on reassuming the shape and conditions in which it was when the impression was last made, to remember the impression, and therefore to do again now what it did then; all intermediate memories dropping clean out of mind, so far as they have any effect upon action. 6. Finally, we should note the suddenness and apparent caprice with which memory will assert itself at odd times; we have been saying or doing this or that, when suddenly a memory of something which happened to us, perhaps in infancy, comes into our head; nor can we in the least connect this recollection with the subject of which we have just been thinking, though doubtless there has been a connection, too rapid and subtle for our apprehension.