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any previous knowledge of what Dr. Priestley had done, and he gave it the name of empyreal air, from its powerful influence in supporting flame. But, instead of entering into the history of such discoveries, and of the processes by which they were made, a few of the properties possessed by the different ingredients of which our atmosphere is composed may be simply stated.

The air of the atmosphere, then, is found to consist chiefly of two very opposite principles or fluids, termed oxygen gas, and nitrogen gas, along with a very small proportion of fixed air, or carbonic-acid gas.

If any portion of the atmosphere, such as the air in our apartments, be supposed to be divided into an hundred equal parts, twenty-one of these parts will be oxygen gas, about seventy-eight nitrogen, and a hundredth part, or, according to some chemists, a thousandth part, will be fixed air, or carbonic-acid gas. In the first place, a few remarks shall be offered on the nature and properties of oxygen gas.

This gas, like common air, is colourless, invisible, and elastic, and capable of indefinite compression and expansion. Its peculiar and distinguishing properties are :- 1st. It is essential to combustion, and is the only principle with which we are acquainted by which flame can be supported. When acting by itself, it produces the most rapid conflagration of all combustible substances. If a lighted taper be let down in a jar of oxygen gas, it burns with

such splendour that the eye can scarcely bear the glare of light, and, at the same time, produces a much greater heat than when burning in common air. If a piece of iron wire, a watch-spring, or a steel file, armed with a piece of wood, or phosphorus, in an inflammable state, be put in this gas, the steel will take fire, throwing out sparks, and producing the most brilliant appearance, almost dazzling the eye with their splendour. In the next place, it is essential to the support of animal life ; for it has been proved by many experiments, that no animal can exist for a single moment in any kind of air which does not contain a certain portion of oxygen; so that man, and all the other ranks of animated beings, may be said to depend upon this substance, not only for their comforts, but for their very existence.

Again, the basis of oxygen gives the acid character to all mineral and vegetable salts, from which property its name is derived; for the term oxygen literally signifies, the generator of acids. In short, oxygen is the vehicle of heat to the animal system-it imparts the red colour to the blood in its passage through the lungs-it constitutes the basis both of the atmosphere which surrounds the earth, and of the water which forms its rivers, seas, and oceans; for water is found to be nothing else than a combination of two kinds of air, oxygen and hydrogen gas. It pervades the substance of all the vegetable tribes, and enables them to perform their functions. In combination with

the different metals, it serves the most important purposes in the useful arts; and, on the whole, may be considered as the most extensively useful, and the most powerful and energetic agent in the system of nature.

Oxygen gas may be procured from a variety of substances, particularly from nitre, manganese, and the red oxyde of mercury, and also from vegetables immersed in water, and exposed to the solar rays. It is heavier than common air, nearly in the proportion of eleven to ten; one hundred and sixteen cubic inches of oxygen are found to weigh about thirtynine grains, while the same quantity of common air weighs only thirty-five and a half grains.

One of the most extraordinary effects of oxygen appears when it is combined with nitrogen in a certain proportion, so as to form what is commonly called nitrous oxyde. This gas consists of sixty-three parts nitrogen and thirty-seven parts oxygen. When it is put into a bladder, and inhaled into the lungs, by means of a pipe, and shutting the nostrils, it produces an extraordinary elevation of the animal spirits-involuntary muscular motion --a propensity to leaping and dancing-involuntary bursts of laughter-a rapid flow of vivid and agreeable ideas, and a thousand delightful emotions, without being succeeded by any subsequent feelings of languor or debility. When Mr. Southey, the poet, inhaled this gas, he declared that it produced in him sensations perfectly new and delightful. His

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first sensations were a kind of dizziness, so as to produce a fear of falling. This was succeeded by a laugh which was involuntary, but highly pleasurable, accompanied with a peculiar thrilling in the extremities perfectly new,

and with the most delightful sensations. For many hours after this experiment, he imagined that his taste and smell were more acute, and is certain that he felt unusually strong and cheerful.

In professor Silliman's American Journal of Science, we have the following account of the effects of this air on one of the professor's students, at Yale College, New Haven. person on whom the experiment was made, was a man of a mature age, and of a grave character. For nearly two years previous to his taking the gas, his health was so very delicate, and his mind so gloomy and distressed, that he was obliged almost entirely to discontinue his studies. In this state of debility, he inhaled about three quarts of the nitrous oxyde. The consequences were, an astonishing invigoration of the whole system, and the most exquisite perception of delight. These were manifested by an uncommon disposition for mirth and pleasantry, and by extraordinary muscular power. The effects of the gas were felt without diminution for at least thirty hours ; and, in a greater or less degree, for more than a week. But the most remarkable effect was upon the organs of taste. Before taking the gas, he felt no peculiar choice in the articles of food; but, immediately after that event, he manifested a taste for such things

only as were sweet, and, for several days, ate nothing but sweet cake. His singular taste was, indeed, carried to such excess, that he used sugar and molasses, not only upon his bread and butter and lighter food, but even upon his fresh meat and vegetables; and this he continues to do (says the narrator) at the present time, although eight days have elapsed since he inhaled the gas.

His health and spirits since that time have been uniformly good, and he attributes the restoration of strength and mental energy to the influence of the nitrous oxyde. He is quite regular in his mind, and now experiences no uncommon exhilaration, but is habitually cheerful, whereas, before, he was habitually grave, and even, to a degree, gloomy and melancholy."

The writer has inhaled this gas, and can attest its pleasing and exhilarating effects. It produced a disposition to laughter, which no consideration could resist, and a wish to flee from the apartment in which the experiment was performed, that laughter might be indulged without restraint. It produced, likewise, an agility and a tendency to skip and jump; and, during its effect, a flow of pleasing ideas passed through the mind, and the lapse of a few seconds seemed to be magnified into as many hours. He has witnessed its effects both on the male and on the female sex. He has seen a little grave man, possessed of a meek and well-cultivated mind, capering through a room with all the airs of a king, brandishing his staff, and

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