the utmost limits of Europe, and to hold at stations as remote as Dublin, Petersburg, and Milan. It became therefore a question of great interest in the extension of this system to still more distant stations, to determine whether there were any, and what limits to this accordance. This.question was determined by the very first results of the observations recently established by the British Government; and the observations now laid before the Section were selected as elucidating it in a very marked manner. These observations were those of the declination and horizontal magnetic intensity observed at Brussels, Milan, Prague, Toronto, and St. Helena, on the 29th of May 1840; and at Dublin, Toronto, St. Helena, and Van Diemen's Land, on the 29th of August of the same year. The magnetical disturbances which occurred on these days were among the most considerable which had been as yet observed. On the former days the declination at Toronto underwent a sudden change, amounting to 1° 52′ in about twenty minutes of time, while the disturbance of the horizontal force was so great as to carry the magnet beyond the limits of its scale. On the latter day, the greatest change of the declination amounted to 1° 26' at Toronto, and to 1° 18' at Dublin. The greatest change of the horizontal intensity at the former station amounted to '028, or about th part of the whole intensity; while at Dublin the change was even greater, and extended beyond the scale of the instrument. It is probable that an attentive comparison of the curves may lead to many important results; but there are some which appear upon a cursory inspection, which Mr. Lloyd said that he should now notice. The first of these was, that the greater magnetic disturbances appeared to be synchronous at the most distant stations. This important fact is exhibited much more evidently in the changes of horizontal intensity than in those of declination; and, if verified by further comparisons, leads to the conclusion, that the principal forces which disturb the magnetic equilibrium of the earth are not of local agency. The next circumstance which merited attention was, that the order of the changes was no longer regulated by the same law, at very remote stations; the representative curves exhibiting none of that similarity already referred to, which was shown within the limits of Europe, and the epochs of the successive maxima and minima presenting no agreement whatever. This important fact was first brought to light in the course of a series of simultaneous observations, made by Professor Bache at Philadelphia, and by himself at Dublin, in November 1839, in the hope of determining differences of longitude by means of the corresponding movements of the magnet at the two stations. The changes observed in the observations at present under consideration were, however, far greater in magnitude, and placed the phænomenon in a much stronger light. The last circumstance to which Mr. Lloyd invited the attention of the Section was, that the curves of horizontal intensity presented a much nearer agreement at remote stations than those of declination; from which it may be inferred, that a true knowledge of the nature and laws of the disturbing causes will be better attained by the examination of intensity changes (including, of course, those of the vertical intensity) than of those which are dependent solely on the direction of the acting forces. There were many other points of minor interest suggested by the examination of these curves; such as the appearance of a correspondence in some of the minuter changes at all the stations, although the resemblance in the greater changes was obliterated. If this should prove to be anything more than a mere fortuitous coincidence, the result might be expected to lead to some important conclusions with regard to the acting forces.

Professor Lloyd then laid upon the table the curves representing the changes of magnetic declination, observed at Cambridge University (Massachusetts) by Mr. W. C. Bond, on the term-days of May and October 1840. The corresponding observations made at the magnetical observatory at Toronto, by Lieut. Riddell, were laid down in a curve, in connexion with the latter. The results exhibited the same close agreement in the forms of the curves, and in the epochs of the successive maxima and minima, as had been already noticed in Europe, although (as before remarked) all resemblance between these and the European system of changes is nearly obliterated. New Cambridge is distant about 500 miles from Toronto; the mean declination there is 9° 20' west.

On Sea Compasses. By the Rev. T. DURY.

In this communication Mr. Dury stated some of the results to which the Rev. Dr. Scoresby, in the continuation of his magnetical researches, has arrived, and

which, with Mr. Dury, he had lately the honour of submitting to his Royal Highness Prince Albert. The points treated of were

The defective condition of ordinary needles employed in sea-compasses, and the method used by Dr. Scoresby to test their condition, by applying them to a highlymagnetized hardened bar of the best cast steel.

The nature of the needles which Dr. Scoresby recommends to be substituted for the former. They are hardened throughout, and previous to being used, are tested by being applied to the bar already mentioned.

The application of delicate needles and large bar-magnets to measure the thickness of rocks, &c., and other materials, in mines, railway tunnels, &c.

The construction and method of magnetizing of a pair of bar-magnets, containing 192 thin steel plates fourteen inches long and one and a half inch broad, bound together with tape. They are very unusually powerful.

On the Influence of Mountains on Temperature in the Winter in certain parts of the Northern Hemisphere. By THOMAS HOPKINS.

It was stated by Mr. Hopkins, that between the latitudes of 40° and 70° north, there is in the same parallels a great difference of temperature, particularly in the winter, amounting in some cases to as much as 40° or even 50° of Fahrenheit. The western coasts of the two continents are much warmer than the eastern, and as the winds generally blow from the sea to the western coasts, it has been inferred, that the prevailing winds passing over sea to the western coasts, and over land to the eastern, was the cause of the difference in the temperature. This inference is not, however, in accordance with facts, as the low temperature is not proportioned to the distance from the western coast.

Hadley's theory represents the tropical atmosphere as rising and flowing over at the top towards the polar regions, and returning when cooled, flowing along on the surface of the earth. This inequality of temperature in the atmosphere would cause an upper current to flow north, and an under current to flow south. But the unequal velocities of the different parts of the earth's surface from the equator to the pole modify the course of these currents, and make the upper a south-west and the lower a north-east current, as shown by lines on a Mercator's chart.

This theory, true in its leading principles, does not account for what occurs on the earth's surface, because it does not take in all the causes that are in operation, which causes materially modify the general results.

The Polar current, in flowing from the north-eastern part towards the south-west, meets with elevations of the land, and is consequently, along a diagonal stripe in the direction of the general currents, obstructed in its progress, and sometimes stopped, and obliged to turn back as an upper current towards the pole; while beyond the obstruction, nearer to the equator, the tropical or upper current not being met by a polar current along this line, flows towards the obstruction, from whence it returns, partially cooled, as an under current.

In the New world, the ridge of mountains which extends from Mexico by the Rocky Mountains to the Frozen Ocean, crosses the diagonal line of the great atmospherical currents, and constitutes such an obstruction as that described.

In the Old world similar ridges extend from the southern point of the Himalaya Mountains to the Swiss Alps, including the range of the Himalaya, Hindoo Koosh,· Central Asia, Armenia, Circassia, the Carpathian Mountains, and the Illyrian and Swiss Alps, and the climates found to the north-east of these chains are materially different from those which exist to the south-west.

The greatest differences of climate in those parts are found in the beginning of winter, and are, it is presumed, caused by the different quantities of atmospheric steam condensed in the respective parts.

Over the tropical seas a quantity of steam exists in the atmosphere sufficient to give a dew-point of 80°, making the steam one forty-eighth part of the whole atmosphere. This steam, which if all condensed into water, would give a depth of about nine inches, is regularly carried in the autumn and the beginning of the winter, when the northern hemisphere is cooled, from the tropical regions in a north-east direction towards the polar regions, or towards some obstructing elevation of the

land, and is to a great extent condensed; and to its condensation we are to look for the great differences of winter climate in the same latitudes of the northern hemisphere.

The steam in the tropical regions of the Pacific Ocean that flows towards the north-east, with the south and south-west winds that prevail in those parts, is carried to the American ridge, and is there condensed. The result is, that the southwest side of this chain of mountains is wet and warm in the winter, from the tropics to Nootka Sound, and still further north. Captain Cook, Lewis and Clarke, Captain B. Hall, and Humboldt, describe the climate of this part in such terms as can leave no doubt of the fact. But beyond this ridge to the north-east we have a different climate in the winter, one as remarkably cold and dry as that on the other side is wet and warm. Captain Parry, Captain Back, and Lewis and Clarke, represent the country in the winter from the shores of the Frozen Sea to the Missouri as very cold and generally dry. Here we trace the effects of the condensation of steam, and of its absence, on the climates of these parts.

In the Old world the same causes produce the same effects. On the south-west sides of the various ridges of mountains, the weather is in the autumn and early part of winter very wet and warm for the latitudes. This is particularly seen in Hindoostan and the south-west coast of Italy, while to the north-east of these mountains the climate is cold and dry, over Poland, Russia, Central Asia, and Siberia.

The very heavy rains which fall to the south of the Himalaya Mountains indicate the great condensation of steam that takes place in that part of the world; and the effect produced on the climate is remarkable. The valleys are habitable to a great elevation; and Major Archer states that wheat is grown at a height of 13,000 feet in latitude 32° north, whilst Humboldt represents 1300 feet as the greatest height at which wheat can be grown in Teneriffe, a place four degrees more south. But when the steam that is in the atmosphere is all, or nearly all, condensed against the sides of elevated ridges, it is evident that it cannot carry its warming influence further north. Hence the part of the globe between these ridges and the polar regions will, in the autumn and winter, be dry and very cold.

In continuation, the author illustrated his views by supposing cases of great changes of the elevation of land and the distribution of land and water on the globe. From the whole inquiry he concludes, that the relative situations of land and water are not the cause of the great differences of climate in corresponding latitudes; but that the great differences in the winter climates of certain parts of the northern hemisphere are attributable to elevations of land intercepting and condensing atmospheric steam, and thus rendering certain parts wet and warm, while cutting off the supply from more northern parts leaves them dry and cold.

On the Temperature of the Air in York Minster. By JOHN PHILLIPS,

F.R.S., G.S.

It may be remarked, that the vastness and loftiness of the interior of York Minster render the air within it, in a great degree, free from violent local draughts, and yet subject to a continual gentle circulation. At the time when the observations now to be noticed were made, there was no heating apparatus in the church: the lights used were a few scattered tapers. The observations were made in the interval from April 8, 1808, to July 31, 1811. There is an interruption from April 27 to May 21, 1810, owing to the absence of the observer, and a few single days are left without observation. From April 8, 1808, to July 12, 1808 (inclusive), the hour of observation is not given. Afterwards it is given for each day, the hours varying from 11 to 5; the far greater number are taken at about 1, and a sufficient proportion about 2 and 3, to render the mean of the whole about 2 P.M., or nearly the epoch of maximum daily temperature in the open air. The observations are registered to half and one-fourth degrees, and, as far as can be judged from inspection, appear to be very faithfully recorded. The following are the deductions:-1. The comparative mean annual temperature within and without York Minster. 2. The comparative mean monthly temperature of the interior of York Minster, and the mean monthly, and mean maximum monthly temperature of the surrounding atmosphere. 3. The comparative epochs of mean annual temperature for the same conditions.

0:4898

Air within the Minster warmer than without......
General mean temperature of York for twenty-five years

TABLE II.

48.2000

It appears that from nearly the end of March to nearly the end of August, the air within the Minster is colder than the mean temperature of the air without; and from nearly the end of August to nearly the end of March, it is warmer. The excess of warmth rather exceeds the deficiency, and the epochs of mean annual temperature are retarded, probably about twelve days, within the Minster,-a result which may be compared with some of the conclusions arrived at by M. Quetelet and Professor Forbes in the prosecution of experiments on subterraneous temperature at small depths.

Further Researches on Rain at York, by JOHN PHILLIPS, F.R.S., and at Harraby, near Carlisle, by JOSEPH ATKINSON, Esq.; with Remarks by Prof. PHILLIPS.

At previous meetings of the Association Mr. Phillips had laid before the Section a considerable series of experiments on the quantities of rain received on equal horizontal areas, at different heights from the ground, and presented as a general view connecting the results, that each drop of rain grows continually larger as it descends through atmospheric strata successively warmer, itself being cold enough to condense on its surface the invisible vapour of water which exists in the air. On this occasion he brought forward some recent experiments, partly his own, and partly made by Mr. Atkinson, from which it might be inferred, that in the further prosecution of this subject, and in the registration of the quantity of rain for any purpose requiring exactness, special care should be taken to choose an unexceptionable situation, and to employ gauges suitable to the object proposed. The statement made by Mr. Phillips at the Glasgow Meeting, of the diminution of the measured quantities of rain, at the small heights of three, six, and twelve feet above the surface, was fully borne out and confirmed by an extract from Mr. Atkinson's register for 1841. Omitting in this year the snowy month of January, we abstract the following measurements of the rain received in funnel-gauges of the usual kind, at Carlisle, on the ground, and at three feet and six feet above:

In contrast with this, Mr. Phillips presented the following table of measures of rain, received on globular gauges (first recommended by the Rev. Dr. Robinson at the Newcastle Meeting of the Association in 1838), at York, on the ground, and three, six, and twelve feet above. A column is also added of the quantity received in a funnel-gauge, three feet above the ground :

By this table it appears, first, that on the average the globular gauges receive nearly twice as much rain as the horizontal funnel-gauge; secondly, that from the ground to a height of six feet, the quantity in those gauges seems not decidedly to vary, beyond limits which may be permitted by small errors of the instrument, or local irregularities; thirdly, that at a height of twelve feet more rain is received than at any of the stations nearer the ground. This singular result the author is at present disposed to view as due to a purely local cause; the situation of the gauges being such, that the lower gauges may be believed to be partly sheltered from the wind by shrubbery, and in consequence, during wind, the rain drops be supposed to fall upon them, in lines deviating less from vertical lines than on the upper gauge. The consequence of such conditions on such gauges would be as the experiments indicate. Mr. Atkinson had previously begun to employ in his series one globular gauge of twelve inches diameter, at a height of six feet; and at this same height he had placed one horizontal funnelgauge of twelve inches diameter, another of 18 inches diameter, and a third funnelgauge of twelve inches diameter, with the opening inclined 45°, and turned constantly to face the wind. The comparative quantities received by the twelve- and eighteeninch horizontal, and the twelve-inch inclined gauges, appear as follows:

Supposing the graduations employed in the registration correct, the larger gauge