was pure, as we would expect a priori, for it arises from the decomposition of the carbonic acid, which contains no azote, it could be obtained in sufficient quantities, in the summer season, for chemical experiments. A small handful of the healthy leaves of Datura stramonium, Phytolacca decandra, and Polygonum aviculare, were separately exposed, eight hours, to the light of the sun, in one hundred and twenty cubic inches of pump-water, which was known to contain carbonic acid, and in the same quantity of boiled and distilled water, impregnated with this air.

From six to eight cubic inches of oxygen gas were obtained from the leaves of each plant.

Phosphorus, inflamed over water, in one hundred parts of this gas, absorbed 70 parts: the remaining 30 parts were azotic air, as appeared by the nitrous test.

Three measures of nitrous gas were added to one of this oxygenous air. The first gave an absorption of 100, the se cond 105, the third 0.

Two cubic inches of this oxygen gas, exploded in the eudiometer of Volta, with four cubic inches of hydrogen gas, left two cubic inches of inflammable and azotic air.

From whence came this azotic air with which the oxygen gas was so highly contaminated? Was it separated by the light and heat of the sun from the water, or was it excreted by the leaves?

As it is difficult, and perhaps impossible, to throw off all the azotic air which water contains, by boiling or distilling it; and as the Galvanic influence, passed through boiled and distilled water, always separates a considerable quantity of azotic gas from it, there is no doubt but that this air was contained in the water.

The contamination, however, is so great, that the oxygen gas, procured in this manner, cannot be used in nice experi

ments.

A third method which presented itself of obtaining pure oxygen gas was from the oxyd of manganese.

This metallic substance often contains carbonate of lime, always azotic gas, and frequently carbonic acid, which it absorbs from the atmosphere.

Two ounce measures of sulphuric acid, diluted with a pint of water, were boiled one hour upon half a pound of the oxyd of manganese, in fine powder, in a glass retort, the mouth of which entered a jar, filled with water, and placed upon the shelf of an hydropneumatic tub. Fifty cubic inches

of air were obtained, forty-six of which were carbonic acid gas, and four azotic air. The acid being washed away from the oxyd, a portion of it was exposed to heat in an iron tube, and it afforded oxygen air perfectly free from carbonic acid gas.

Phosphorus, placed in twenty cubic inches of this air, over water, absorbed nineteen inches of it, and left one cubic inch of azotic gas.

The same quantity of oxygen air, from the same kind of manganese, upon which no acid had been boiled, treated in the same manner, left two cubic inches of azotic gas.

Two cubic inches of oxygen air, from the purified manganese, exploded with four of hydrogen gas, left one fourth of a cubic inch of oxygen and azotic air.

The oxygen air from manganese, upon which no acid had been boiled, treated in the same manner, left one cubic inch of hydrogen and azotic gas.

Four measures of nitrous air were added to one of the oxygen gas, from the purified manganese: the first gave an absorption of 120, the second 145, the third 115, and the fourth

15.

Four measures of the same air were added to one of the oxygen gas, from manganese not boiled in the acid. The first gave an absorption of 120, the second 130, the third 100, the fourth 0.

Phosphorus, fired in 100 parts of the oxygen gas, from the purified manganese, left three hundred parts of a measure of azotic air.

One hundred parts of the oxygen gas, from the manganese to which no acid had been added, treated in the same manner, left five parts of azotic air.

The quantity of azotic gas contained in this oxyd of manganese was very small, and the greater part of it was thrown off with the carbonic acid, by the sulphuric acid and water.

Exposing the purified manganese, in an earthen retort, to a red heat, the oxygen air obtained was found to contain ten per cent. azotic gas. A part of the atmospheric air entered the pores of the heated retort, and mixed with the oxygen gas: hence an earthen vessel never should be used when it is necessary to have oxygen air very pure.

Although many writers say that oxygen gas can be procured perfectly pure from the hyperoxygenated muriate of pot-ash, yet I never could obtain it of a higher degree of purity than the air from the oxyd of mercury, from turbith mineral by VOL. I.

P

pot-ash, or from manganese boiled in sulphuric acid and water. Upon comparing the oxygen gas from these three substances, no difference could be observed between them. The oxygen air, from the oxymuriate of pot-ash, devoured nearly four measures of nitrous gas, yielded two per cent. azotic air, when phosphorus was fired in it, and left one fourth of a cubic inch of azotic and hydrogen gas, when two cubic inches of it were exploded with double the quantity of hydrogen gas.

My experiments on this subject exactly coincide with those of Dr. Priestley, and it is highly probable that oxygen gas never has been obtained in a state of perfect purity.

There are several other oxyds of mercury, besides that from turbith mineral, from which oxygen air may be obtained very pure, as mercurius precipitatus per se, the oxyd from red precipitate, boiled in a solution of pot-ash, to free it from every particle of nitric acid it may contain; but these preparations are very expensive.

Having examined two hundred cubic inches of the oxygen air from nitre, as it was produced, the first few cubic inches were found to be mixed with six per cent. of azotic air, which gradually increased until it amounted to forty parts in the hundred, which the last portions contained; so that the air from this salt scarcely deserves the name of oxygen gas.

ARTICLE III.

OBSERVATIONS on VACCINATION: By JOHN REDMAN CoxE, M. D. of Philadelphia.

N the 9th of May, 1803, I vaccinated Molly Allen, a

On the 90 off 25 years of age, at the Philadelphia Dis

pensary. She was at this period, in every respect, in perfect health. The infection I employed was a year old, had been carefully taken from a very fine pock on the eighth day, and preserved between glass, coated with gold-beater's skin. As this was merely for an experiment, I was not surprised at its failure. On the 18th I repeated the attempt with infection of the 10th day, two days old, by two punctures of the right arm. This took effect in one of the punctures, and a fine pock commenced its career. On the eighth day I obtained infection; at which period there was great local itching, with commencing tumefaction of the axillary glands, and fe

rough_gown.

brile irritation. The pock was not much larger than is common at this stage. On the ninth day, from the great tumefaction of the skin around the pock, I was satisfied of the existence of the areola, though I could not perceive it accurately till the following day, when the pock had been irritated by a rough gown. On the ninth day I renewed the vaccination from her own pock, about two inches below the first, by a single puncture. I was at this period pursuing some experiments to ascertain the constitutionality of the disease by the progress of a second vaccination, as proposed by Mr. Bryce, when the symptoms are so moderate as not to be discernible.* Although the constitutional disease had here commenced its career, and though the areola of the first pock was in existence, it took effect, and advanced with such rapid strides, that its areola came on as early as the third day, when the pock was only beginning to evince its successful progress. Its scab came off on the 6th of June, or the twelfth day from the deposition of the infection: whilst the scab of the first adhered till the 10th. On the tenth day several little fiery-looking pimples appeared around the original pock, some within and some without the areola, which disappeared in a few days. She had been very inattentive, by using her arm in the freest manner, to wash, &c. in opposition to my strict advice. She complained much of pain in the axilla, the glands of which continued to enlarge. The pock was now nearly half an inch in diameter, very perfect, and turgid with a limpid fluid. From the irregularity of the patient I did not again see her till the fourteenth day. She informed me she had the preceding day struck the pock against the lock of the safe (for provisions), which had broken it, and the matter had oozed out in great abundance, as might be readily expected; for it was now considerably upwards of an inch in diameter. The second pock appeared to be fully one fourth of an inch, though it was barely the termination of the fifth day. In the primary pock a scab had commenced in the centre, and was about one third of an inch over. The edges were plump,† well defined, and elevated at least a quarter of an inch, with a hard tumid base of between three and four inches diameter. It was accompanied with great

This practice I uniformly employ when in my option, and I cannot but recommend it to the serious consideration of every friend to vaccination.

† Excepting the part struck, from which a considerable quantity of fluid pozed.

itching, and the febrile symptoms were urgent for several days, though by no means so much so as I expected from the appearance of the disease and its repeated irritations. I now or dered a smart purgative, and abstinence from animal food, with the local application of lead-water; and without much difficulty (although considerable irritation was produced by two or three subsequent blows upon it) it pursued its course to a favourable issue; for by the 17th day the scab was more than half an inch over; whilst the circumference was greatly augmented, and had commenced an irregular desiccation, owing, I presume, to the continual rupture of the edges from blows, &c. Hence the uneven appearance of the outline of the pock at this period. In a few days the scab was perfectly formed, and fell off in separate pieces; owing, I imagine, to the con stant moisture applied to it, which had allowed the cuticle to contract irregularly. I was, however, fortunate enough to obtain the largest portions, which I sent to Dr. Jenner, and which will serve to evince, in conjunction with the Mammoth, that neither nature nor disease are in this country disposed to belittle themselves. Jesting apart: That this was a case of a pock of a natural size in the patient, independent of external causes, is evinced, from its having arrived to a considerable size before any injury whatever was sustained. The second vaccination from herself proves the same. By this no injury was sustained, and in the short space of six days it had progressed beyond the usual size of the vaccina. The small fiery looking pimples I mentioned had nothing to do with its augmentation, as they disappeared in a very short period after their first accession. I have repeatedly seen pock which have gone on increasing for several days after the areola had declined, and the scab had commenced in the centre, but I do not think any of them exceeded six tenths of an inch.

I do not know if any peculiar deductions can be drawn from this curious instance of uncommon magnitude. It may; however, serve to prevent uneasiness in the minds of physicians or their patients, by assuring them of an equally fortu nate termination with a smaller case of the disease, even under circumstances of repeated irritation. It was to me, for several days, a source of anxiety, which I would wish to prevent in others.

One circumstance in this case deserves to be noticed, though it is by no means singular: I allude to the successful event in one puncture, and the complete failure of the other, though similar in every respect. Does this arise from an absolute in