is watered by the rivers Exe and Otter; and comprises about 200 square miles: the latter, separated from that of Exeter by a ridge of high land, extends in an opposite direction to the Bristol Channel. Aylesbury stands in a vale, abounding in rich pasturage, and watered by the Thames as it flows through Buckinghamshire The Trent also has its vales, particularly in that part of the county of Nottingham which borders on Lincolnshire and Leicestershire.

The rivers of England have been enumerated in the article BRITAIN; more particular descriptions of their courses belong to their respective places in the alphabet: and the canals of this country form a large feature in our article INLAND NAVIGATION.

No country is richer, for its size, in mineral waters. Those of Bath, Buxton, Bristol, and Cheltenham, have already fallen under our notice: Harrowgate, Matlock, Scarborough, and Tunbridge Wells complete the catalogue of the principal ones, and will each be found distinctly treated. At Gloucester a chalybeate spring has recently been discovered, more strongly impregnated than either those of Cheltenham or Leamington. We must not omit to notice the aluminous chalybeate water of the S. S. W. of the Isle of Wight. This contains sulphate of iron and sulphate of alumen: there are also some portions of carbonic acid gas, sulphate of lime, sulphate of magnesia, sulphate of soda, muriate of soda, and silicia: but these ingredients are rendered wholly imperceptible to the palate by the superior portions of iron and alumen. These impregnations are much stronger than are to be met with in any other mineral water of England; and even than those of Hertfell-water in Scotland. The sulphureous waters of Gilsland, in Cumberland, consist of muriate of soda, sulphureted hydrogen gas, azotic gas, and carbonic gas. The

Greatest height Least height

saline waters of Leamington Priors, in Warwickshire, are also in considerable repute and much frequented. The medicinal springs issuing from the Malvern Hills in the counties of Worcester, Gloucester, and Hereford, are of various qualities; but principally chalybeate. They do not contain any uncombined vitriolic acid, volatile alkali, or metallic salt; but are slightly impregnated with fixed air, some common air, selenites, and a little unneutralised calcareons earth.

There is a chalybeate spring at Southampton, at the bottom of Orchard Street, resembling that of Tunbridge Wells. The component parts are steely particles, marine salts, an oily matter, an ochreous substance, a volatile vitriolic spirit, too subtile for analysis, and a simple fluid. The Nottington mineral spring, near Weymouth, contains hepatic, phlogisticated, and fixed air, the digestive salt of Sylvius, vegetable alkali, magnesia, &c., and strongly resembles the Moffat water in Scotland.

Of the ever-varying but healthy climate of this country we have observed that July and August are its warmest, and December and January its coldest months. In the former Fahrenheit's thermometer seldom rises above 85° or 86°, the general maximum of the year being 81° or 82°; and in the latter it seldom sinks lower than 14° or 15°, though it has been known to descend below 0°. The thermometer has been long supposed to attain the greatest height a little west of the metropolis; but this, as we shall presently show, is a mistake. The north-eastern counties are subject to a greater degree of cold than those on the north-west. The north and south of England differ less in the temperature of winter than in that of summer. The greatest and least heights of the thermometer, at the following places, have been thus given:

clusive, at London, to be 43.5°; while at Dawlish, on the south coast of Devonshire, it is 45-3°, and at Ilfracombe, on the shore of the Bristol Channel, as high as 59°. From November to March the mean temperature, at London, is 42.6°; at Penzance, in Cornwall, 48·1°. From January to March, at London, 37.9°; at Penzance, 48.5°; and at Sidmouth, in Devonshire, 41.7°. During February and March, in the metropolis, 41-5; at Clifton, 42.5°. From October to December, in the capital, 47°; and at Sidmouth, 45.7°. In the most sheltered parts of Devonshire the mean winter temperature exceeds that of London by about 1.5°; while, during the coldest months, the temperature at Penzance is, according to this writer, higher than at London by 4.5°.

Mr. Howard, who has directed his particular attention to the climate of London and its neighbourhood, observes, in regard to the law of temperature in such climates as ours, that it is probable the mass of air is similarly affected by the sun's rays, and that the proportion of heat

which it derives from the direct passage of the rays is the same in all seasons. "The accumulation of heat,' says he, 'near the surface of the earth, which we always experience from continued sunshine, is evidently due to the stoppage of the rays at that surface, and to their multiplied reflexions and refractions, in consequence of which they are as it were absorbed and fixed, for a time, in the soil and in the incumbent atmosphere. By this process the earth, when in a cold state in the end of winter, becomes gradually heated to a certain depth as the warm season advances. On the other hand, when the sun declines, in autumn, the soil thus heated acts as a warm body on the atmosphere, and gives out again the heat it has received.' Howard on the Climate of London, vol. ii. pp. 131, 132. Were it not for this effect on the part of the earth,' Mr. Howard continues, 'the heat indicated by the thermometer would probably, on a long average (to obviate the remaining irregularities caused by clouds, rain, wind, and evaporation), be precisely at its maximum and minimum at the solstices, and at the mean at the equinoxes. For the power of the sun is proportionate to the quantity of parallel rays falling on a given area of the earth's surface. And this quantity is greatest when they are vertical, and diminishes as they become more oblique; till in a perfectly horizontal position of the rays it is null.'

It results from these causes, that the maximum and minimum temperatures of our climate, in place of coinciding with the solstices, are removed to a whole month after them; and, in like manner, the mean temperature of the year is developed about a month after either equinox. In consequence of this fact, which is fairly deduced from actual observation, Mr. Howard is led to propose a new division of the seasons, more consonant with the actual phenomena on the earth's surface amid which we live, than the present, which has regard only to the remote causes of temperature, and not to the actual temperature which exists around us. This natural division is effected by 'removing the beginning of the seasons fifteen days from their respective present situations, and placing them at that distance before the equinoxes and solstices.

ham Green, with those recorded in the Philosophical Transactions for thirty years, and which were made at the Royal Society's apartments in London, that the temperature of the air in this metropolis is regularly raised by artificial sources of heat to 2° on the annual mean above that of the immediate vicinity.

Mr. Howard's explanation of this singular difference is the following: That the superior temperature of the bodies of men and animals is capable of elevating, in a small proportion, the mean heat of a city or populous tract of country in a temperate latitude, is a proposition which will scarcely be disputed. Whoever has passed his hand over the surface of a glass hive, whether in summer or winter, will have perceived how much the little bodies of the collected multitude of bees are capable of heating the place that contains them. But the proportion of warmth which is induced in a city by the population, must be far less considerable than that which emanates from fires, the greater part of which are kept up for the very purpose of preventing the sensation attending the escape of heat from our bodies. A temperature equal to that of spring is hence maintained, in the depth f winter, in the included part of the atmosphere, which, as it escapes from the houses, is constantly renewed: another and more considerable portion of heated air is constantly poured into the common mass from the chimneys; to which, lastly, we have to add the heat diffused in all directions from the foundries, breweries, steam-engines, and other manufacturing and culinary fires.' Vol. ii. p. 104. To these direct additions of extraneous heat, Mr. Howard also adds the augmentation derived in summer, from the accumulation of the natural temperature by the artificial condition of the city.

The excess of the city temperature is least in spring and greatest in winter, and seems to belong entirely to the nights, which average 3° warmer than the country, while the heat of the days, owing without doubt,' as he says, 'to the interception of a portion of the solar rays by a constant veil of smoke, falls, in a mean of years, about a third of a degree short of that in the open plain.' The following is the proportional superiority of the London temperature in the twelve different months.

January February

March

April

May

June

July August September October November December

The mean temperature of London, according to Mr. Howard, is 48° 30′ of Fahrenheit, or about 2o less than has usually been supposed. This varies, he says, in different years as much as 4° 30′, and the variations, he very singularly contends, are periodical, and appear to recur in

cycles of seventeen years. We cannot afford space for the detail of the circumstances which led him to form this opinion; but extract from the summary of the work an abridged enunciation of the fact:

'We may consider one of these cycles as commencing either with 1790 or 1800, and ending with 1806 or 1816. In either case, a year of mean temperature begins the cycle, in which the coldest year falls at the end of ten years, and the warmest at the end of seven years, reckoning from the coldest, and thus alternately; both together including a complete revolution of mean temperature from its highest to its lowest extreme (or vice versâ, from the lower to the higher), and back again. The year 1816, which was the coldest of a cycle, appears to have had parallels in 1799 and 1782; and there is every reason to conclude, from present appearances, that the warm temperature of 1806 will re-appear in 1823, which will probably be the warmest, and 1833 the coldest, upon the whole year, of a cycle of seventeen years, beginning with 1807. Vol. ii. p. 289. The greatest heat to which the climate of London is liable is 96°; the greatest cold is -5°: thus the full range of the thermometer is not less than 100°.

A temperature above 80° is almost always

London. Penzance

followed, either in our own or the neighbouring districts, by thunder-storms, which, in their turn, are succeeded by rain and a reduction of heat. Owing to our insular situation, and other causes, even in the coldest season of the year, the medium of the twenty-four hours, upon a long average, does not fall below the freezing point. Continued frost, in winter, is therefore, always an exception to the general rule of the climate.' p. 292. The following is the mean temperature of the different months, in whole numbers, in the vicinity of London: January 34°, February 39o, March 41°, April 46, May 55°, June 58°, July 62°, August 61°, September 56o, October 50°, November 40°, December 37°. -The mean annual range is 72°. The mean diurnal range, or difference between the day and night is 14°; and this varies in the different months as follows, beginning with January, 8°, 10°, 12°, 15°, 17°, 18°, 17°, 17°, 16", 13°, 10°, 8°.

Before we dismiss these comparative estimates of the temperature of our climate, we may compare from the respective works of Dr. Forbes, on the climate of Penzance, and Mr. Howard's Treatise, the mean temperature of the year in London and Penzance. Both works rank with our most accurate and faithful histories of the weather.

London

Max. 56 Min. 8

8288

Penzance Min. 19 26 28 32

It appears, from documents contained in Dr. Forbes's Essay, that the temperature of Penzance retains the same proportional superiority in the colder months over all the places usually esteemed the mildest in our island; for instance, the sea-coast of Devonshire, the Isle of Wight, Clifton, &c.; a fact which well accounts for, and justifies, the resort of consumptive invalids to the western extremity of Cornwall.

In thirteen years the thermometer, at 7 A. M. at Penzance, has only been thirty-seven times below the freezing point; consequently frost is stated to be of rare occurrence; and the exercise of skating entirely unknown among the young men of the place. The average number of days in the year on which snow falls is very little more than two and a half; and, out of the four

78 78 74 68 69 58 42 45 52 50 42 37 28 22

teen years, four are recorded on which no snow fell. As the most unequivocal proofs of the peculiar mildness of the winters, Dr. Forbes, at the end of his paper, gives lists of exotic and indigenous plants growing in the vicinity of Penzance; among which are several which we are not accustomed to see out of the greenhouse. In the open grounds two crops cf potatoes are often produced in the year. But the most striking feature of the climate in this district seems to be its equability.

During the prevalence of north and north-east winds, the barometer is generally highest in England, and lowest when it blows from the opposite points. Its highest range is from May to August: and the following are the extreme and mean results of seven different places.

Mr. Howard has established another curious fact in his researches: viz. the decided influence of the moon on the barometer. By comparing the results of that instrument at the different phases, for a period of ten years, he found that the mercury suffers a depression of about a tenth of an inch, by the influence of the new and full moon respectively; while, at the first and third quarters, the moon's influence is, in respect of position in her orbit, neutral, producing neither elevation nor depression in the barometer.' p. 226. And, by comparing the barometric indications during different periods of the moon's declination, he ascertained that the quicksilver stands considerably above the mean, while the moon is south of the equator, and, in a like proportion, below it, while she is to the north of the equator. On further examining the temperature, winds, rain, &c., in the different periods answering to these varied affections of the moon's path, he ascertained, as might indeed have been expected, that these suffered corresponding, but certainly less uniform, changes.

Our winds blow with the greatest constancy, as well as strength, from the west and southwest, as is evinced by the leaning of the trees, in all parts exposed to its influence, towards the opposite quarters. This is thought to arise from the situation of the island with respect to the Atlantic and the Continent, and the difference of atmospheric temperature between them at certain seasons of the year. Next to these, the east and north-east winds are the most prevalent. It generally blows least from the south and north-west. So great is the inconstancy, however, that in summer it often blows from several points of the compass in the same day. In the maritime parts of England, especially in the south, during warm and settled weather, the seabreeze prevails in the middle of the day, and the land-breeze, morning and evening. In the neighbourhood of London Mr. Howard's observations are, 1.A wind from the north or between that and the east prevails on an average seventy-four out of the 365 days of the year; the extremes being ninety-six and fifty-eight days. 2. A wind from east to west prevails fifty-four days, varying in different years from seventy-two to thirty-four days. 3. A wind from south to west 104 days, varying from 123 to seventy-eight. 4. A wind from west to north 100 days, varying from 124 to eighty-three. 5. Variable winds obtain about

Mr. Howard has a valuable observation on the 'apparent anomaly of a north-west wind, predominating in our wettest season in summer, and a south-west during the autumnal rains.' 'I conclude,' he says, 'from a careful review of the cases, that the former is not the carrier but the condenser of the vapor, which appears to be introduced, at intervals only, from the south and south-east. When the surplus vapor has been disposed of in rain on these occasions, the northwest resumes its sway, the atmosphere recovers its transparency, et claro cernes siivas Aquilone moveri,' Virg. but it is usually not long before the returning clouds indicate the near approach of a new supply of vapor.'

In the decline of the year, the rain appears to originate in a somewhat different way. The great body of the atmosphere is then usually moving with some force from south-west to north-east, while the sun is declining to the southward. An air already turbid from beginning precipitation, is further charged below by an excess of evaporation from the agitation of much watery surface over which it passes. Every calm interval then affords its shower, followed by wind and evaporation again and a succession of gales by night, and cloudy days, characterise the approach to the hibernal season.' Vol. ii. p. 211.

Mr. Dalton estimates the average quantity of rain that falls throughout England at 31-3 inches: at Ware it has been averaged during five years at 236 inches. Mr. Howard gives it in London and the neighbourhood at somewhat above 250 inches. But the Royal Society during eleven years at only 21.25 inches. The quantity is distributed, throughout the year, according to Mr Howard, in the following proportions:

The following years have been the wettest of a series of twenty-three years, and in the order in which they are put down, viz. 1816, 1797, 1807, 1802; and it further appears that the warm years were uniformly dry, or below the average in rain, and the cold years uniformly wet, or above the average.' The proportion of rain by day and night is very different, being no less than one-third more in the latter period,a fact which has been verified in different parts of the kingdom, and which is, doubtless, a beneficent arrangement of that same Providence, which has appointed the day for labor, and the night for rest. The greatest quantity of rain col