The same phenomenon may be observed on ascending into the air.

La Gazette de Mons has published, in relation to a balloon ascension by Mr. Green, some extracts from a report that Dr. B. addressed to the Society of Natural Sciences in London: -

"A curious effect of light," says that physician, "was then presented to us; the air was suddenly illuminated with such a dazzling light, and our eyes acquired such a singular aberration of vision, that all objects lately microscopic acquired colossal proportions, and forms so capricious, that we should have considered ourselves under the influence of a dream if the phenomenon had not been described by the faculty, under the term diachromatopsia.

* Abercrombic, op. cit. p. 65.

"In like manner the race of miners, usually so swarthy on account of the dust of the coal they constantly absorb, appeared to us of a dazzling whiteness; women dressed in black were white as vestal virgins. In the midst of these transformations of colon there glided monstrous forms of goats, mastodons, and rhinoceroses, looking with eyes of wonder on all these pretty women; and there were even turkeys, who flew proudly amongst them. My friend M. believed himself under the influence of hallucination; but Mr. Green told us he had already witnessed a similar spectacle, which appeared to him so extraordinary that he had not dared to speak of it, for fear of being taken for an illuminist. I explained to him that the phenomenon, howsoever wonderful, had already been described by men of acknowledged veracity.

"In ten or twelve minutes, the light diminished, the picture darkened, and was finally extinguished."*

Second Section. - This second division of physical causes, which may give rise to hallucinations, comprises mechanical causes, alcoholic drinks, certain gases, some kinds of plants, and narcotic and venomous substances. Amongst mechanical causes which favor the presence of hallucinations, must be noticed pressure exercised on the organs of sense, their irritation from foreign bodies, concussion of the brain, hanging, abstinence, and starvation.

A miner was buried for twelve days in a gallery, with no nutriment but water, which fell, drop by drop, into his hand. During all this time, he was not depressed; for, whenever he thought of the distress of his wife and children, he heard celestial voices, which calmed his anguish.†

M. Savigny was wrecked in the Medusae frigate. When on the raft, a prey to all (he horrors of famine, he appeared to see earth around him, covered with fine plantations, and was in company with beings most agreeable to his senses. He reasoned on his condition, and felt that the exercise of strong resolution alone could extricate him from this species of deception. Some of his companions in misfortune believed themselves on board the Medusse, surrounded by all accustomed objects; others saw ships, and invoked the aid of those on board, or a raft, on which stood a superb city. M. Correard believed himself to be travelling over the beautiful country of Italy.* M. Savigny remarks, that it was during the night that he and his companions were attacked with dementia. On the return of day, they were much calmer, but darkness brought confusion again into their weakened senses. "I noticed in my own case," he adds, "that my imagination was much more excited in the silence of the night; then, everything appeared unnatural and fantastic, "†

* Debates of the 4th of November, 1850.

† Medical and Physical Journal, by William Hutchinson, February, 1820, vol xliii. No. 252.

Abstinence must have been a powerful aid to the hallucinations of the monks and hermits of the Thebaide.

The influence of alcoholic liquors has been sufficiently demonstrated in what we have said on Delirium Tremens; we will not return to this subject beyond making a simple remark. It is not unusual for persons who have been addicted to drinking, and leave it off suddenly, to become subject to hallucinations; whereas, if they discontinued the practice by degrees, they would not experience any suffering.

The action of deutoxide of azote on the system merits particular attention. Sensations and ideas are simultaneously augmented to a very high degree; the mind gradually loses all or the greater portion of its actual impressions, more especially those which are painful or disagreeable; these are replaced by gay and pleasing images. Sir Humphrey Davy relates that, in an experiment of this kind, he no longer felt any connection with external objects; a series of visible and animated images passed rapidly through his mind, united with words, in such a manner as to produce entirely novel perceptions. "I existed," said he, "in an unknown world of affinities and ideas. On coming to myself, I exclaimed, 'Nothing exists but thoughts; the universe is composed of impressions, ideas, pleasures, and pains.' " The visionary world into which the English savant was introduced was only the personification and vivification of his ideas.‡

* Account of the wreck of the Medusa), 4th edition, 1821, pp. 121,122.

† Essay read in 1818, to the Faculty of Paris, by M. Savigny, Surgeon on board the Medusse frigate.

‡ To these substances must bo added preparations of lead, carbonic acid gas, the white oxide of arsenic, belladonna, hyoscyamus, etc.

Of all substances which act on the organization, in causing illusions and hallucinations, none are more remarkable than opium and haschisch. In a work, entitled The English Opium-Eater, we find a well-written account of the sensations experienced by the author after a prolonged use of this drug.