image of the struck eagle beholding the fatal dart, that had laid him low, feathered with his own pinion.

Experiments are not sufficiently numerous to afford data whereon to make a statement that ozone has any specific effect upon the poisons, which, whilst floating in the air, produce cholera, small-pox, erysipelas, and other zymotic diseases. Should it hereafter be shown that it possesses so invaluable a property, its resemblance to chlorine will be lessened, for this gas has been proved to be thoroughly inefficacious, if not actually injurious, in cholera. "At the time," says Dr. Albers,* "that the cholera hospital was filled with clouds of chlorine, then it was that the greatest number of attendants were attacked.” The same agent was tried in the Small-pox Hospital some years ago; all offensive smell was overcome as usual, but the power of communicating the disease remained behind.

Ozone is insoluble in water,-another point of difference between it and chlorine, which is absorbed by this liquid to the extent of two volumes at 60° under ordinary pressure. Phosphuretted and sulphuretted gases, compounds constantly found in putrid exhalations, are decomposed rapidly by it even at a low temperature. I will conclude these remarks with one more question. Is ozone, when mixed with aqueous vapour, affected like chlorine by light? The reason for my asking this question is the fact that I have, as a general rule, found more ozone developed during the night than by day. It will be interesting to discover the relation between this agent and other meteorological phenomena, such as the wind, temperature, hygrometric and electric state of the atmosphere, &c., a few observations on which have already been quoted from Dr. Moffat's interesting papers on this subject.

Intimately associated with ozone, is the Electric Condition of the Atmosphere, upon which, in its relation to a pestilential state of the season, I shall now make a few remarks. I find from the Meteorological Observations taken at the Royal Observatory * London Med. Gaz. vol. iii. p. 410; Pereira, Materia Medica, 3d ed. vol. i. p. 371.

during the twenty-two weeks of the cholera epidemic of 1854, that the following are the facts, which are proved by the daily register. The total number of days comprehended within the above period was 154.

Positive electricity was shown in 101 days.

The real number of observations would, therefore, be 126. During the decline of the cholera, the greatest amount of negative electricity was developed especially during the week ending November 18, when this kind was exceedingly strong. The tension of the electricity developed throughout this time was in the average "moderately strong." If we compare the above table with the account of the electricity developed during the first twenty-two weeks of the year, when deaths from cholera were hardly ever registered, a strong contrast will present itself.

Positive electricity was shown in 23 days.

These are simple facts. So far they only prove that cholera prevailed at a time when the atmosphere was charged almost daily with positive electricity; and that little or no electricity could be discovered by the apparatus during many of the weeks at the commencement of the year, when this disease had not

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begun to show itself. It must be remembered that these observations were made at Greenwich, where the epidemic raged severely probably, had the observations been made in the centre of the pestilential cloud, the results would not have been very different.

The High State of the Barometer is another remarkable feature in the history of many epidemics; and as the weight of the atmosphere is so materially influenced by the amount of aqueous vapour, perhaps, as we have been discussing moisture in its connection with the south wind, it will not be out of place to notice what has been observed upon this point, although my space will not admit of my going much into detail.

The high state of the barometer during the prevalence of cholera has been remarked, for instance, by Dr. Prout.* Mr. Hingeston, in several of his papers on the state of the weather during cholera, has also observed a similar rise during the late epidemic. I shall quote Dr. Prout in full. "On a particular day, the 9th of February, 1832, the weight of the air suddenly appeared to rise above the usual standard. As the rise was at the time supposed to be the result of some accidental error, or of some derangement in the apparatus employed; in order to discover its cause, the succeeding observations were made with the most rigid scrutiny: but no error or derangement whatever could be detected. On the days immediately following, the weight of the air still continued above the standard; though not quite so high as on the 9th of February, when the change was first noticed. The air retained its augmented weight during the whole time these experiments were carried on,—namely, about six weeks longer. The increase of the weight of the air observed in these experiments was small, but still decided and real. The method of conducting the experiments was such as not to allow of an error, at least to an amount so great as the additional weight, without the cause of that error having become apparent. There seems,

* Bridgewater Treatises, viii. p. 353.

therefore, to be only one mode of rationally explaining this increased weight of the air of London in February 1832; which is, by admitting the diffusion of some gaseous body through the lower regions of the atmosphere of this city, considerably heavier than the air it displaced. About the 9th of February, the wind, which had previously been west, veered round to the east, and remained chiefly in that quarter to the end of the month. Now, precisely on the change of the wind the first cases of epidemic cholera were reported in London, and from that time the disease continued to spread. That the epidemic cholera was the effect of the peculiar condition of the atmosphere, is more, perhaps, than can be safely maintained; but reasons which have been advanced elsewhere lead the writer of this treatise to believe that the virulent disease termed cholera was owing to the same matter which produced the additional weight of the air. *** The foreign body, therefore, diffused through the atmosphere of London in February 1832 was probably a variety of malaria." I shall make one or two remarks upon the above statement of Dr. Prout. This gentleman lays much stress upon the height of the barometer in February 1832. Daniell, in his Meteorological Essays,* gives an abstract of his observations made at Chiswick from 1826 to 1842 inclusive, whence I derive the following facts:—' -That the greatest height of the barometer in February 1832 was 30-591 inches, or several parts of an inch lower than it was in the years 1827, 1829, and 1840; and that its mean height was 30 109, or higher than it ever reached during the seventeen years, with the exception of the year 1834: this last fact, coupled with the first, indicates a certain amount of steadiness in the height of the atmosphere. Dr. Prout also remarked that the change in the wind was followed by the appearance of cholera. The reader must compare his statement with that of Professor Daniell, who gives the number of days during the month that each wind prevailed: thus-N. 6, NE. 5,

* Vol. ii. pp. 338 to 365.

E. 3, SE. 4, S. 6, SW. 3, W. 1, NW. 1: so that the points from N. by the E. prevailed for eighteen days, whilst those from the S. by W. only blew on eleven. Mr. Hingeston has observed that the northerly wind, with a tendency to the north-east, is conducive to the occurrence of cholera, while, on the contrary, he believes that the south-west wind, with plenty of rain, is conducive to healthiness. Connected with the high state of the barometer, is the fact that during February 1832 less rain fell (0.23 inch) than was registered in the same month for all the seventeen years. During the cholera year of 1854, the barometer readings were very high: at Highfield House Observatory, at an elevation of 181 feet, they exceeded the mean readings of seven years during the months February, March, April, August, and September, during which last two months the epidemic was at its acme. In March it reached to 30.928 inches. At Greenwich, the mean readings of the barometer for the whole year were in excess (+082) of the average of thirteen years, and those for the several quarters were also in excess, with the exception of the one including the months October, November, and December,—the quarter in which the cholera continued to subside, and at last disappeared. I have thought it right to place the above scattered facts before the student, not so much for the sake of admitting that any theory can be built upon them, as to draw his attention to what eminent men have observed, which in itself is sufficient to induce him to direct his observations to a point in meteorology, in its relation to disease, of the greatest importance, if not as a practical, at least as a scientific question, the solution of which may prove of the greatest benefit to mankind.

Droughts (Αὐχμῶν δέγενομένων τοὺς ὑπόπροσθεν χρόνους).Droughts are stated to have prevailed in the year preceding the one under discussion, and it is remarkable that many epidemics have occurred after very dry seasons; for instance, the plague at Constantinople in 1541 succeeded to the drought of