nearly midway between the extremities of the land, forming the western boundary of North Africa and Europe, which runs in a general direction S.S.W. and N.N.E.; and it is highly probable the centres of the crests of the north-west systems of waves pass near its locality, having considerably subsided as they passed over England. The general direction of the flowing of the south-westerly waves would be that of the land above-mentioned, Brussels being the general meeting-point of the two systems.

In addition to the observations having immediate reference to the great symmetrical wave, and extending through October, November and December, I have been furnished with observations from Helstone in Cornwall by M. P. Moyle, Esq., and also with observations from Newcastle-on-Tyne by George Muras, Esq.; from August 1845 to December 1846, they have been made at 9 A.M., 3 P.M. and 9 P.M., and contain all the requisite data for exhibiting the gaseous pressure only, reduced to the level of the sea. As the localities are admirably situated for investigating the transits of the southwesterly waves, I have made arrangements for the discussion of these obser vations, with especial reference to the wind at both stations, as elucidatory of Prof. Dove's parallel currents. This discussion is not yet sufficiently advanced to present any results to the present meeting.

PROGRESS.

We are now in possession of materials for examining the great symmetrical wave of November, on the occasions of its transits in the years 1842, 1845 and 1846; we also possess a few sets of observations for 1843 and 1844. Of the above-named years the examination of 1842 has proceeded to the greatest extent; the postscript accompanying my last report contains the latest information relative to the great wave of 1842, with the exception of the discussion of the St. Petersburgh and Geneva observations, on a plan similar to the discussion of Mr. Brown's observations, as detailed in my last report. These stations being considerably removed from those forming the subjects of the discussion just alluded to, the observations require a par ticular mode of treatment in order to incorporate them with the others, and by means of the whole, to trace the law of continuity of the separate waves, and thus follow them in their progress over the continent of Europe as they respectively pass onward towards the north-east and south-east. A very careful discussion of the observations at each station in connection with every other set, from stations to the westward hitherto examined, in order to obtain a correct notion of the distribution of pressure, and the progress of the lines of maxima and minima over so vast a space as we have now materials for examining, is necessary before the observations at stations to the eastward are discussed, otherwise we lose many of the essential features of the waves, which become exceedingly modified in their progress, and we fail to detect them at the more remote stations. The Russian observations, as before stated, will add most materially to our knowledge of these movements; but the discussion of them on the plan above-mentioned, must necessarily involve much labour. I have as yet only combined the observations from St. Petersburgh and Geneva, with those recorded on page 141, and of this extended group they form the most eastern stations. This combination has proceeded through the first eight days of November, and appears fully capable of explaining all the barometric movements during those eight days. It will however be desirable to postpone the further report of this part of the inquiry until the observations at more of the Russian stations have been severally discussed, with reference to the more extended group, as I apprehend some important and valuable information will be elicited especially illustrative of the transit of the waves over eastern Europe.

The barometric curve at any one station being a compound effect resulting from the transit of two or more individual atmospheric waves, before we shall be able fully to explain the symmetrical curves, as they occur year after year in the southern and south-eastern parts of our island, as well as the decrease of oscillation especially from the north-west towards the nodal point, Brussels, and assign the numerical expression of its increase in different directions from this nodal point, it will be necessary to study the individual waves, and endeavour clearly to apprehend them in the totality of their existence; until we can do this we shall be unable to assign the true causes of the symmetrical curve. To assist in this part of the inquiry, we have already alluded to the importance of extending the range of observation, both in a northerly and southerly direction, but especially towards the south-west: observations from the Mediterranean, as suggested by Sir John Herschel, will also be extremely important.

A most important point appears to be developing itself by means of such observations as form the subject of the present report: two localities of great interest are brought prominently into view. The observations from the north-west appear most strongly to indicate that, somewhere in that direction, the origin of the great barometric disturbances, a centre of oscillation giving rise to the waves that pass onwards towards the south-east, is to be sought. We have already mentioned Iceland as an important station, and under the aspect just contemplated its importance is considerably increased; its proximity to the coast of Greenland will render it still more valuable as a connecting link between the great American and European systems of waves. From the point of disturbance, wherever situated, the greatest decrease of oscillation is noticed towards the south-east, or, more strictly speaking, on a line from the Orkneys to Brussels; this line more or less ranges along the eastern coasts of Scotland and England, and conducts us to the locality of least oscillation, the nodal point, Brussels, already noticed. Were it not for the south-westerly system of waves, which are continually crossing those from the north-west, the numbers representing the decrease of oscillation from the Orkneys to Brussels could readily be ascertained; but before we can do this in a satisfactory manner we must be well-acquainted with the phænomena presented by the south-westerly system, and especially ascertain if this set of waves also exhibits a decrease of oscillation with its amount, should it do so. Under this aspect, observations from the south-west will possess a much greater value, than by considering them only as important to determine the longitudinal directions of the crests of the north-west waves. Of the grant of £10 placed at my disposal, I have expended £6 9s. 3d. In order to carry on the investigation, especially with regard to the Russian observations, I most respectfully solicit a continuance of the grant.

W. R. BIRT.

EXPLANATION OF PLATES. PLATE I. Consists of a selection of twenty curves, that are so arranged as to exhibit the modifications of form, decrease of oscillation and approach to symmetry which are observable as we proceed from the north-west, the locality of greatest barometric disturbance, towards Brussels, the nodal point of the two principal European systems of atmospheric waves. In the first five curves, which are from stations bordering on the Atlantic, and embracing nearly the whole of the north-western boundary of the British Isles, the greater amount of oscillation is well seen. The decrease of oscillation, the change of form, and the approach to symmetry, become apparent in the Scotch curves, as we recede from the area of greatest disturbance; and

these features are more strikingly developed as we proceed across England to Kent, which presents us with the most symmetrical curve, that obtained from observations at Ramsgate, the lowest in the Plate; the smaller altitude of this curve, especially as compared with the north-western curves, is very striking.

PLATE II.-Fig. 1. Exhibits the great symmetrical wave as it passed London, and is projected on a scale suitable for exhibiting its essential features.

Fig. 2. Exhibits the wave as it passed Ramsgate: the scale, which is contracted in one direction and enlarged in another in order to exbibit the minor inflections and to trace the variation of form as we proceed to the north-west, is the same as in Pl. I.: the symmetry principally consists in the greater development of the anterior subordinate waves, by which they are raised nearer on a level with the posterior; this obtains only at Ramsgate.

Fig. 3. Exhibits the form of the wave as it passed St. Vigean's. These curves, Ramsgate and St. Vigean's, are placed in juxtaposition, to show more distinctly the points of similarity and difference obtaining on the line of greatest deviation from symmetry, which in the present instance ranges more or less with the eastern coast of England and Scotland.

Fig. 4. Exhibits graphically the differences between the Stornoway
(Western Isles) and Ramsgate curves.

Fig. 5. Exhibits graphically the differences between the Newcastle and
Helstone curves.

Fig. 6. Exhibits graphically the differences between the Stornoway and
Helstone curves.

PLATE III.-Fig. 7. Exhibits the Galway curves.

Fig. 8. Exhibits the alternations of pressure at Limerick, Helstone and
Jersey.

Fig. 9. Exhibits the pairs of curves, Ramsgate, Jersey, Stornoway and
Galway.

Fig. 10. Exhibits the opposite barometric movements at St. Petersburgh
and Geneva, arising from the slopes of the south-westerly waves
Nos. 1 and 3, which traversed Europe during the first eight days
of November 1842.

Temperature Tables, by Prof. W. H. Dove, Cor. Mem. of the British Association with Introductory Remarks by Lieut.-Col. EDWARD SABINE, General Secretary.

THE following pages contain the numerical elements of an investigation on which Professor Dove has been employed for several years past; they consist of the mean temperatures of the different months of the year, of the seasons, and of the year itself, at above 800 stations on the surface of the globe, with the differences between the summer and winter seasons, and the hottest and coldest months, and a notice of the number of years during which the observations have been continued in each case, and of the hours of observation. The original memoir, in which this assemblage of the results of observation will be embodied, will appear in the volume of the Transactions of the Berlin Academy of Sciences, which will be published in the course of 1848; in that memoir the temperatures will be expressed in degrees of Reaumur's scale, which is more commonly used in Germany than either Fahrenheit's or the Centigrade; the transformation of these into Fahrenheit's scale, in which they appear in the subjoined tables, is Professor Dove's own work; a labour undertaken and executed by him expressly for the convenience of the members of the British Association, and of those who profit by its publications. Whether we regard this sacrifice of time, on the part of a person who is undoubtedly in the first rank of those who are advancing by the sure path of induction into hitherto uninvestigated regions of meteorological science, simply as an evidence of his desire to promote the general advancement of science; or, as perhaps we may permit ourselves to do, as an evidence of that general desire, of which he has given so many proofs, strengthened in this particular case by the recollection of the respect and regard with which his presence was welcomed at the Cambridge meeting of the British Association in 1845,-we are bound, in either case, to express our acknowledgements for a labour which certainly augments greatly the value of the tables to British readers.

The mean temperatures have not been corrected for the diurnal variation corresponding to the particular hour or hours at which the observations were made, excepting in a few instances, which are marked red. (for reduced) in the column showing the hours of observation; but nine tables have been added, containing in degrees of Fahrenheit the corrections to the true mean quantities for nine stations differing widely in geographical circumstances, computed by Bessel's formula

is prefixed, and north when there is prefixed, and west when Where N.Y. occurs in

tx=u+u'(sin x+U')+u"(sin 2x+U")+u'''(sin 3x+U'''). The latitudes are south when the sign is no sign. The longitudes are east when there is no sign. The heights are in British feet. the column showing the hour of observation, it signifies that the results have been computed by the formula

N.Y.=a+2b+2c+a'

6

in which a is the observation at 6 A.M., b at 3 P.M., c at one hour after sunset, and a' at 6 A.M. the following day. D, in the final column, signifies that the mean temperatures of the several months at the stations so distinguished, are taken from one or other of four memoirs published by Professor Dove in the Transactions of the Berlin Academy, entitled Über die nicht periodischen Änderungen der Temperaturvertheilung auf der Oberflache der Erde.' The seasons are the usual meteorological seasons, winter consisting of December, January and February, and so forth.

Besides the correction already noticed for the diurnal variation of the temperature corresponding to the particular hour or hours at which the observations at a station have been made (which has only been applied in a few specified instances in the subjoined tables, as it appeared preferable to give generally the original determinations independent of the corrections), the mean temperatures derived from the particular year or years during which the observations were continued at each station, will require in each case to be corrected for the non-periodic variation of the temperature in the year or years in question. On this subject the reader is referred to the preface and to pp. 34 to 59 of Professor Dove's fourth memoir (entitled as above) in the Transactions of the Berlin Academy for 1847. From the mean temperatures corrected for the diurnal and for the non-periodic variations, Professor Dove proposes to construct isothermal curves for each month of the year, and has expressed his intention of taking a future opportunity of communicating the curves to the British Association; but he is desirous that in the mean time a few of the more striking phænomena which have been brought into notice by this extensive assemblage and intercomparison of the results of observation should be briefly indicated.

1. The most novel at least, if not the most important of these, is the remarkable cosmical fact which they establish, of the existence of an annual variation in the aggregate mean temperature at the surface of the globe, having its period of maximum during the sun's northern declination, and of minimum during his southern declination.

If we compare the temperatures at stations in the southern hemisphere with those of stations of corresponding latitude in the northern hemisphere, we find that it is generally the fact, that the sum of the simultaneous mean temperatures at the two stations in the months of June, July and August (or of those months which constitute the northern summer and the southern winter), is greater than the sum of the simultaneous mean temperatures in December, January and February, or in the months which constitute the northern winter and southern summer. Let us take for example the comparison of the mean temperatures in the seasons at Toronto, latitude 43° 40' N., and Hobarton, latitude 42° 53' S., derived in each case from five years of hourly observation at the magnetical and meteorological observatories at those stations; we have from 37,296 observations at Toronto, and 37,320 at Hobarton (Sundays not being days of observation) the mean temperatures of the different seasons as follows:

We perceive by this comparison that the mean temperature of the months of December, January and February at Toronto + the mean temperature of the same months at Hobarton, exceeds by 22°7 the mean temperature of the months of June, July and August at Toronto + the mean temperature of the same months at Hobarton.

If a similar comparison be made of stations in South America, South