This affection has always attacked me at sea with greater severity than on shore. I have already hinted, that during the paroxysms, I have frequently possessed that degree of consciousness, that I have been aware that my servant was knocking at my door, announcing to me the hour of the morning. Experience has repeatedly proved to me that I was correct in my perceptions; often too have I found by experience, that I was widely mistaken. The instance I am going to relate happened on board one of his Majesty’s ships at Spithead: I was lying in my cot, labouring under a paroxysm of Night-Mare; it was broad day-light, and I could perceive distinctly all the objects in my cabin, which came within the range of vision; I was likewise conscious of labouring at the moment under this disagreeable malady, when I heard distinctly a person approach the cabin door, and immediately after knock at it, and a well known voice of a Quarter-master, who was often in the habit of calling me, after repeating my name, informed me that the Captain wished to see me immediately. I was unable to make any answer to this, although I attempted it, and both the knocking and the message were repeated, I do not now remember whether twice or thrice; I heard, however, the person retire from the cabin door. As soon as I recovered, I rose and hastened to obey the summons which I had received, but was soon informed that the Captain was not on board, and that no messenger of any kind had been near my cabin. These instances I have adduced, to shew how very strong a sense of conviction they impress on the mind of their reality, when there is any degree of probability in the transaction, and the evidence afforded by the senses is no less striking when the vision itself is ever so extravagant. When, however, the patient awakes immediately out of the Night-Mare, he is generally at once convinced of the hallucination; unless in cases of extreme probability like the last mentioned instance. But when the paroxysm of Night-Mare goes off, and the patient continues asleep for some time after, the confusion of ideas which succeed on waking is very perplexing. If he has had any vision during the Night-Mare, the impression of it remains on the mind like any transaction which has really occurred, and he has no method of ascertaining the true nature of the case, but by considering the degree of probability, and comparing it with his past experience of similar hallucinations; if he has no such experience, it is ten to one whether he will ever arrive at a true understanding of the affair.