Siljeström has described this meeting of the two currents. Their alternation was marked here by similar conditions of temperature, as it had been at Vienna. At Mariestadt the thermometer rose from -9°-4 to 37°-4 on the 29th, and fell again on the same day to 8°.6. At Lilla Edet the barometer fell 141 inches between the 27th and 29th, while the N. gave way to the SW. wind, the temperature at the same time rising 45°, from -10°.3 to 34°4. When the snowstorm set in the barometer began to rise, and reached its former level on the 30th, while the thermometer sank to 1°.6.

This was the last effort of the northern current, as it subsequently gave way to the southern current so completely, that on February 6 the barometer in Central Europe reached a level which was almost the lowest on record. In Berlin it stood, on February 6, 2·10 inches lower than on January 21. At Stettin the difference was 2.22 inches, and even in Florence 1.46. The simultaneous elevation of temperature was so great, that, while the five-day mean' for the period from January 31 to February 4 was 23°.9 at St. Petersburg, 21°3 at Mitau, 13°.7 at Arys, below its value, derived from the average of several years' observations, the succeeding mean, for the 5th to the 9th February, was too high to the extent of 6°2 at St. Petersburg, 10°-4 at Mitau, and 9°3 at Arys. The increase of temperature at the three stations is found to be 25° 2, 25° 0, and 19°-7 respectively. This southern current was so persistent, that at many stations in North Germany the minimum level of the barometer was not reached until the 22nd.

* Om Snöstormen den 29 Januari, 1850 (On the Snowstorm of January 29, 1850), in his Afhandlingar och Smärre Uppsatser i Fysiska och Filosofiska Aemnen (Treatises and Shorter Papers on Physical and Philosophical Subjects), 1857, p. 356.

The extension of this second minimum is given in the following table. Throughout the whole area there was a thaw, with southerly winds. The figures indicate the depression, in inches, referred to the mean for January, which nearly agrees with that for the whole year:

At the following stations the barometrical reading was above its mean level on the same day:

-

Salem (U.S.A.) +0·525

The five-day mean is relatively very high over the whole area, with the exception of the Ural, where the cold was not interrupted. At Mitau the excess was 10°.44; at Breslau, 7°.64 ; &c.

In contrast to the elevated temperature in Europe, we

* At the stations to which an asterisk is prefixed the minimum occurred on the 7th.

find that February 6 was the coldest day at Providence in North America, and, at the same time, that of the barometrical maximum of the year (0-829 inches above the mean height for the year). Similarly, at Cambridge, near Boston, the barometer stood 0-833 inches above its mean level, with a thermometrical minimum of -3°1. At Savannah the excess was 0.559 inches on the 6th, and the lowest temperature 25° on the 5th. At Chapel Hill, S. Carolina, the excess was 0.533 inches, while the thermometer fell to 11°5 on the 5th. At Muscatine in Wisconsin the barometrical maximum occurred on February 3, with a temperature of -13°9. At Greenlake the lowest temperature was -13°.9 on the 4th. We obtain the same results from the graphical delineation in the Fourth Report.' The barometrical maximum appeared in the Western States earlier than in those on the coast of the Atlantic, where, however, the oscillation was more extensive. In the latter States the barometer was very low at all the stations up to the 3rd, and then rose suddenly to a maximum on the 6th. These facts give us, on a great scale, an instance of a compensation between the distribution of pressure and temperature in a horizontal direction; and we should be able to investigate it thoroughly if the American observations had been published in a manageable form. There is more information relative to this great atmospherical disturbance to be derived from the American Almanack,' which contains the numerical values of the monthly means and monthly extremes of the barometer and thermometer for a few stations, than from the curves for fifty-five stations, which are printed on huge sheets, and of which there is not a single syllable of explanation contained in the 240 4to. of Introduction. Mr. Espy, instead of furnishing a pages Report, as the title-page promises, talks, as usual, of

nothing but himself and his theory. In this work, Mr. Espy challenges me to discuss his theory, in which he attributes the fall of the barometer to the latent heat set free by the condensation of vapour during a courant ascendant shower. I should be prepared to do this if Mr. Espy would first explain the fact which was established by me nine years before he propounded his theory -viz. that the motions of the barometer and thermometer on the W. side of the windrose are in the opposite direction to those on the E. sidea fact which in itself is sufficient to upset his theory; or would even pay any attention to my publications on the subject, which he has never deigned to do. The phenomena of most common occurrence that most extensive condensations of aqueous vapour take place in those parts of the torrid zone which are not visited by hurricanes, without any change of the barometer, of any extent, being observable; that in the temperate zone the barometrical oscillations are most extensive in winter, at which period the action of the courant ascendant disappears entirely in proportion to that of the ordinary atmospherical currents; that, as the instance just quoted proves, a barometrical minimum may advance over an entire continent in one direction, while a maximum is advancing over another continent in the opposite direction; that the yearly barometrical curve for the interior of continents is of a totally different form from that for the coasts of the oceans,--show us so clearly the necessity of making a distinction between the local courant ascendant and the great horizontal currents, whenever we attempt to discuss atmospherical phenomena, that this must always be presupposed when we treat of any theory which is intended to embrace the phenomena of the atmosphere. With reference to the fact established by me that the rarefaction which takes place over

Asia in the summer is the cause of the monsoon - Mr. Espy informs me, at p. 135, that the Monsoon of India has a SW. direction, and therefore does not blow towards the interior of Asia, neglecting, as he always does, to take any notice of the influence exerted by the rotation of the earth round its axis. The words of Redfield are exactly suited to this objection, who, when Mr. Hare charged me with having, in adherence to Redfield's theory, maintained that the axis of an advancing cyclone was inclined forwards, forgetting that such an inclination would lift the base in the rear,' replied, ' It seems hardly to require an answer.' The reason that I have never answered Hare's 'Strictures on Prof. Dove's Essay on the Law of Storms' is, that as long ago as in the year 1828 I had published a paper on Thunderstorms, and therein given at length my reasons for considering that the electrical phenomena which accompany heavy showers were only secondary phenomena. There was, accordingly, no need for me to controvert an explanation which interprets the origin of storms, on the assumption that the atmosphere is placed between two oceans of electricity of opposite kinds, one of which is terrestrial, the other celestial.

The disturbance which we have been considering did not terminate in February, for there were violent storms in March and April. Martin has discussed them fully in A Memoir on the Equinoctial Storms of March-April 1850; an Inquiry into the Extent to which the Rotatory Theory may be applied,' 1852, 8vo.

SNOWSTORM IN DECEMBER 1850.

A good example of this type of storms is to be found in a snowstorm which has been investigated by Spassky.*

*Note sur la Tempête d'Hiver qui a fait oeaucoup de Désastres à Kalouga, Toula, et à Kursk entre le 9-11 Dec., 1850 (Note on the Snowstorm which