Madmen, do not always continue in the same furious or depressed states: the maniacal paroxysm abates of its violence, and some beams of hope, occasionally cheer the despondency of the melancholic patients. We have in the hospital some unfortunate persons, who are obliged to be secured the greater part of their time, but who now and then become calm, and to a certain degree rational: upon such occasions, they are allowed a greater range, and are admitted to associate with the others. In some instances the degree of rationality is more considerable; they conduct themselves with propriety, and in a short conversation will appear sensible and coherent. Such remission has been generally termed a _lucid interval_. When medical persons are called upon to attend a commission of lunacy, they are always asked, whether the patient has had a _lucid interval_? A term of such latitude as interval, requires to be explained in the most perspicuous and accurate manner. [The circumstances which probably occasioned the employment of this term are pointed out in the chapter which enumerates the causes of insanity.] In common language, it is made to signify both a moment and a number of years, consequently it does not comprize any stated time. The term _lucid interval_ is therefore relative. As the law requires a precise developement of opinion, I should define a _lucid interval_ to be a complete recovery of the patient's intellects, ascertained by repeated examinations of his conversation, and by constant observation of his conduct, for a time sufficient to enable the superintendant to form a correct judgment. Unthinking people, are frequently led to conclude, that if, during a short conversation, a person under confinement shall bewray nothing absurd or incorrect, he is well, and often remonstrate on the injustice of secluding him from the world. Even in common society, there are many persons whom we never suspect, from a few trifling topics of discourse, to be shallow minded; but, if we start a subject, and wish to discuss it through all its ramifications and dependancies, we find them incapable of pursuing a connected chain of reasoning. In the same manner insane people will often, for a short time, conduct themselves, both in conversation and behaviour, with such propriety, that they appear to have the just exercise and direction of their faculties: but let the examiner protract the discourse until the favourite subject shall have got afloat in the mad man's brain, and he will be convinced of the hastiness of his decision. To those unaccustomed to insane people, a few coherent sentences, or rational answers, would indicate a lucid interval, because they discovered no madness; but he, who is in possession of the peculiar turn of the patient's thoughts, might lead him to disclose them, or by a continuance of the conversation, they would spontaneously break forth. A beautiful illustration of this is contained in the Rasselas of Dr.