ENCYCLOPEDIA BRITANNICA. C CLI-CLI YLICHY, or CLICHY LA GARENNE, a village or township | of France, in the department of Seine, situated on the right bank of the river, immediately to the north of the ramparts of Paris, of which it may almost be said to be part. It is the seat of a number of extensive industrial establishments, engaged in the manufacture of steam engines, chemical stuffs, and glass. The village is of high antiquity, and was the residence of some of the early kings of France. Its church was built in the 17th century under the direction of the famous Saint Vincent de Paul, who at that time had charge of the cure. Population in 1872. 14,599. CLIFTON, a watering-place and fashionable resort of England, in the county of Gloucestershire, forming practically a part of the city of Bristol. It is situated on the castern heights above the gorge of the lower Avon, whicli | divides it from the county of Somerset,-partly occupying a spacious table-land about 250 feet above the sea, and partly an abrupt declivity which sinks down to the once fashionable district of the Hotwells, on the same level as Bristol. Three ancient British earthworks bear witness to an early settlement on the spot, and a church was in existence as far back as the time of Henry II., when it was bestowed by William de Clyfton on the abbot of the Austin canons in Bristol; but, with the exception, perhaps, of Mardyke House, in 'Hotwells, there are no longer any architectural vestiges of an earlier date than the 18th century. Of the churches the most important are St Andrew's parish church, an ungainly structure rebuilt in 1819; All Saints, erected in 1863 at a cost of £32,000, after the designs of G. E. Street, and remarkable for the width of its nave and the narrowness of its aisles; and the Roman Catholic pro-cathedral church of the Holy Apostles, with a convent and schools attached. Among the other buildings of note may be mentioned the Victoria Rooms, which are used for concerts and other public assemblies, the Fine Arts Academy, dating from 1857, and Clifton College, a well-designed cluster of buildings in the Gothic style, founded in 1862 by a limited liability company, and giving education to 550 boys. The famous suspension bridge across the Avon, designed by Brunel and commenced in 1832, was completed in 1864. It has a span of 702 feet, and the roadway is 245 feet above high water; the total weight of the structure is 1500 tons, and it is calculated to stand a burden of 9 tons per square inch. Since it was opened a village called New Clifton has grown up on the opposite bank. The once famous hot springs of Clifton, to which, in fact, the town was indebted for its rise, are no longer frequented. They issue from an aperture at the foot of St Vincent's Rock, and the water has a temperature of about 76° Fahr. The population of Clifton in 1712, the date of the second edition of Sir Thomas Alleyne's work on Gloucester, was only 450; in 1841 it amounted to 14,177; in 1857 to 17,634; in 1861 to 21,375; and in 1871 to 26,364. In the last-mentioned year there were 10,319 males and 16,045 females.. The average annual mortality is about 14 per 1000. CLIMATE. The word Climate, or kλiua, being derived from the verb kλivew, to incline, was applied by the ancients to signify that obliquity of the sphere with respect to the horizon from which results the inequality of day and night. The great astronomer and geographer Ptolemy divided the surface of the globe, from the equator to the arctic circle, into climates or parallel zones, corresponding to the successive increase of a quarter of an hour in the length of midsummer-day. Within the tropics these zones are nearly of equal breadth; but, in the higher latitudes, they contract so much that it was deemed enough to reckon them by their doubles, answering consequently to intervals of half an hour in the extension of the longest day. To compute them is an easy problem in spherical trigonometry. As the sine of the excess of the semidiurnal arc above a quadrant is to unity, so is the tangent of the obliquity of the ecliptic, or of 23 28', to the cotangent of the latitude. The semidiurnal arcs are assumed to be 91° 52', 93° 45', 95° 37', 97° 30', &c., and the following table, extracted from Ptolemy's great work, will give some general idea of his distribution of seasons over the surface of the globe. The numbers are calculated on the supposition that the obliquity of the ecliptic was 23° 51 20", to which, according to the theory of Laplace, it must have actually approached in the time of Ptolemy. They seem to be affected by some small errors, especially in the paral lels beyond the seventeenth, as the irregular breadth of | the zone abundantly shows; but they are, on the whole, more accurate than those given by Varenius. Climate in its modern acceptation siguifies that peculiar state of the atmosphere in regard to heat and moisture which prevails in any given place, together with its meteorological conditions generally in so far as they exert an influence on animal and vegetable life. The infinitely diversified charactor which climate displays may be referred to the combined operation of different causes, which are chiefly reducible to these four-distance from the equator, height above the sea, distance from the sea, and prevailing winds, which may thus be regarded as forming the great bases of the law of climate. Of these causes which determine climate incomparably the most potent is distance from the equator. The same sunbeam which, falling vertically, acts on a surface equal to its own sectional area is, when falling obliquely on the earth, spread over a surface which becomes larger in inverse proportion to the sine of the obliquity. Consequently less and less heat continues to be received from the sun by the same extent of surface in proceeding from the equator toward the poles; and this diminution of heat with the increase of obliquity of incidence of the solar rays is enhanced by the circumstance that the sun's heat, being partially absorbed in its passage through the atmosphere, the absorption is greatest where the obliquity is greatest, because there the mass of air to be penetrated is greatest. Hence arise the broad features of the distribution of temperature over the globe, from the great heat of equatorial regions, falling by easy gradations with increase of latitude, to the extreme cold of the poles. If the earth's surface were uniform, and its atmosphere motionless, these gradations would run everywhere parallel with the latitudes, and Ptolemy's classification of the climates of the earth would accord with fact. But the distribution of land and But the distribution of land and water over the earth's surface and the prevailing winds bring about the subversion of what Humboldt has termed the solar climate of the earth, and present us with one of the most difficult, as certainly it is one of the most important problems of physical science, viz., the determination of the real climates of its separate regions and localities, and the causes on which they depend. down for the height of the snow-line, it can only be ascertained by observation. Speaking generally it sinks little from the equator to 20° N. and S. lat.; from 20° to 70° it continues to fall equably, but from 70° it falls rapidly to 78°, where it is at sea-level. The following are a few of the more noteworthy of the exceptions On the north side of the Himalayas it is about 4000 feet higher than on the south side, owing to the greater depth of snow falling on the south side and the greater dryness of the climate of Tibet, resulting in a more active evaporation from the snows and stronger sun-heat on the north side, to which is to be added the comparative want of vegetation on the north side, thus favouring a more rapid melting of the snows. The snow-line is higher in the interior of continents than near their coasts, the rain. fall there being less and the heat of summer greater; and similarly, owing to the greater prevalence of westerly over easterly winds in many regions of the globe, it is higher on the east than on the west sides of continents. In South America the snow-line rises very considerably from the equator to 18° S. lat. and more so, markedly, on the west than on the east slopes of the Cordilleras, because of the smaller amount of precipitation of the west side of this mountain range. It is as high in 33° as in 18° S. lat., but south of 33° it rapidly sinks owing to the heavy rains brought by the westerly winds which begin to prevail there. In the south of Chili it is 6000 feet lower than among the Rocky Mountains at the same distance from the equator, and 3000 feet lower than in the same latitudes in Western Europe. It is impossible to overestimate the importance of the snow-line as one of the factors of climate in its relations to the distribution of animal and vegetable life. Glaisher, in his balloon ascents, made observations of temperature at different heights, the results of which may be thus summarized. Within the first 1000 feet the average space passed through for 1° was 223 feet with a cloudy sky and 162 feet with a clear sky; at 10,000 feet the space passed through for 1° was 455 feet for the former and 417 feet for the latter; and above 20,000 feet the space with both states of the sky was 1000 feet nearly for a decline of 1°. It must be noted, however, that these rates of decrease refer to the temperature of the atmosphere at different heights above the ground, which are in all probability altogether different from the rates of decrease for places on the earth's surface at these heights above the level of the sea-the problem with which climatologists have to deal. Observation shows, as might have been expected, that the rate at which the temperature falls with the height is a very variable quantity,-varying with latitude, situation, the state of the air as regards moisture or dryness, and calm or windy weather, and particularly with the hour of the day and the season of the year. In reducing temperature observations for height, 1° for every 300 feet is generally adopted. In the present state of our knowledge this or any other estimation is at best no more than a rough approximation, since the law of decrease through its variations requires yet to be stated, being in truth one of the most intricate and difficult problems of climatology awaiting investigation at the hands of meteorologists. Among the most important climatic results to be determined in working out this problem are the heights at which in different seasons the following critical mean temperatures, which have important relations to animal and vegetable life, are met with in ascending from low-lying plains in different regions of the world, viz., 80°, 75°, 70°, 65°, 63°, 60°, 58°, 55°, 50°, 45°, 39° (the maximum density of fresh water), 32° (its freezing point), and 20°. The decrease of temperature with height is perceptibly felt in ascending mountains, and is still more evident in the snow-clad mountains, which may be seen ever in the tropics. The snow-line marks the height below which all the snow that falls annually melts during summer. The height of this line above the sea is chiefly determined by the following causes-by distance from the equator; by the exposure to the sun's rays of the slope of the mountain, and hence, in northern latitudes, it is higher on the south than on the north slopes of mountains, other things being equal; by situation with reference to the rain-bringing winds; by the steepness of the slope; and by. the dryness or wetness These results, which only affect the mean daily temof the district, Since, then, no general rule can be laidperature in different seasons, and which are due exclusively to differences of absolute height, though of the greatest | possible practical importance, yet leave untouched a whole field of climatological research-a field embracing the mean temperature of different hours of the day at different heights, for an explanation of which we must look to the physical configuration of the earth's surface and to the nature of that surface, whether rock, sand, black soil, or covered with vegetation. Under this head by far. the most important class of conditions are those which result in extraordinary modifications, amounting frequently to subversions, of the law of the decrease of temperature with the height. This will perhaps be best explained by supposing an extent of country diversified by plains,. valleys, hills, and table-lands to be under atmospheric conditions favourable to rapid cooling by nocturnal radiation. Each part being under the same meteorological conditions, it is evident that terrestrial radiation will proceed over all at the same rate, but the effects of radiation will be felt in different degrees and intensities in different places. As the air in contact with the declivities of hills and rising grounds becomes cooled by contact with the cooled surface, it acquires greater density, and consequently flows down the slopes and accumulates on the low-lying ground at their base. It follows, therefore, that places on rising ground are never exposed to the full intensity of frosts at night; and the higher they are situated relatively to the immediately surrounding district the less are they exposed, since their relative elevation provides a ready escape downwards for the cold air almost as speedily as it is produced. On the other hand valleys surrounded by hills and high grounds not only retain their own cold of radiation, but also serve as reservoirs for the cold heavy air which pours down upon them from the neighbouring heights. Hence mist is frequently formed in low situations whilst. adjoining eminences are clear. Along low-lying situations in the valleys of the Tweed and other rivers of Great Britain laurels, araucarias, and other trees and shrubs were destroyed during the great frost of Christmas 1860, whereas the same species growing on relatively higher grounds escaped, thus showing by incontestible proof the great and rapid increase of temperature with height at places rising above the lower parts of the valleys. This highly interesting subject has been admirably elucidated by the numerous meteorological stations of Switzerland. It is there observed in calm weather in winter, .when the ground becomes colder than the air above it, that systems of descending currents of air set in over the whole face of the country. The direction and force of these descending currents follow the irregularities of the surface, and like currents of water they tend to converge and unite in the valleys and gorges, down which they flow like rivers in their beds. Since the place of these air-currents must be taken by others, it follows that on such occasions the temperature of the tops of mountains and high grounds is relatively high because the counter-currents come from a great height and are therefore warmer. Swiss villages are generally built on eminences rising out of the sides of the mountains with ravines on both sides. They are thus admirably protected from the extremes of cold in winter, because the descending cold air-currents are diverted aside into the ravines, and the counter-currents are constantly supplying warmer air from the higher regions of the atmosphere. Though the space filled by the down-flowing current of cold air in the bottom of a valley is of greater extent than the bed of a river, it is yet only a difference of degree, the space being in all cases limited and well defined, so that in rising above it in ascending the slope the increased warmth is readily felt, and, as we have seen, in extreme frosts the destruction to trees and shrubs is seen rapidly to diminish. The gradual narrowing of a valley tends to a more rapid lowering of the temperature for the obvious reason that the valley thereby resembles a basin almost closed, being thus a receptacle for the cold air-currents which descend from all sides. The bitterly cold furious gusts of wind which are often encountered in mountainous regions during night are simply the out-rush of cold air from such basins. The two chief causes which tend to counteract these effects of terrestrial radiation are forests and sheets of water. If a deep lake fills the basin, the cold air which is poured down on its surface having cooled the surfaco water, the cooled water sinks to a greater depth, and thus the air resting over the lakes is little if at all lowered in temperature. Hence deep lakes may be regarded as sources of heat during winter, and places situated near their outlet are little exposed to cold gusts of wind, while places on their shores are free from the severe frosts which are peculiar to other low-lying situations. The frosts of winter are most severely felt in those localities where the slopes above them are destitute of vegetation, and consist only of bare rock and soil, or of snow. If, however, the slopes be covered with trees, the temperature is warmer at the base and up the sides of the mountain, the beneficial influence of forests consisting in the obstacle they offer to the descending currents of cold air and in distributing the cold produced by terrestrial radiation through a stratum of the atmosphere equalling in thickness the height of the trees. Hence as regards strictly local climates, an intelligent knowledge of which is of great practical value, it follows that the best security against the severity of cold in winter is afforded where the dwellings are situated on a gentle acclivity a little above the plain or valley from which it rises with an exposure to the south, and where the ground above is planted with trees. When it is borne in mind that in temperate climates, such as that of Great Britain, the majority of the deaths which occur in the winter months are occasioned or at least hastened by low temperatures, it will be recognized as of the most vital importance, especially to invalids, to know what are the local situations which afford the best protection against great cold. In truth, mere local situations may during periods of intense cold have the effect of maintaining a temperature many degrees above that which prevails close at hand-a difference which must mitigate suffering and not unfrequently prolong life. In addition to mere elevation and relative configuration of surface, the land of the globe brings about important modifications of climate in the degree in which its surface is. covered with vegetation or is a desert waste. Of all surfaces that the earth presents to the influences of solar and terrestrial radiation an extent of sand is accompanied with the most extreme fluctuations of climate, as these are dependent 'on the temperature and moisture of the air; whilst on the other hand, extensive forests tend to mitigate the extremes of temperature and distribute its daily changes more equably over the twenty-four hours. As regards the influence of the sun's heat on the temperature of the air, attention is to be given almost exclusively to the temperature of the extreme upper surface of the earth heated by the sun with which the air is in immediate contact. Badly conducting surfaces, such as sand, will evidently have the greatest influence in raising the temperature of the air, for the simple reason that the heat produced by the sun's rays being conveyed downwards into the soil with extreme slowness must necessarily remain longer on the surface, in other words, remain in immediate contact with the atmosphere. Similarly at night, the cooling effects of terrestrial radiation being greatest. on sandy surfaces, the climate of sandy deserts is characterized by nights of comparatively great cold. These daily alternations of heat and cold are still further intensified by the great dryness of the air over extensive tracts of sand. In warm countries the surface temperature of sandy deserts often rises to 120°, 140°, or even to 200°, and the shade temperature has been observed as high as 125°. It is this hot air, loaded with particles of sand still notter, and driven onwards by furious whirlwinds, which forms the dreaded simoon of the desert; and the irritating and enervating sirocco of the regions bordering the Mediterranean is to be traced to the same cause. It is in the deserts of Africa, Arabia, Persia, and the Punjab that the highest temperature on the globe occurs, the mean summer temperature of these regions rising to and exceeding 95°. The extreme surface of loam and clay soils is not heated during day nor cooled during night in so high a degree as that of sandy soils, because, the former being better conductors, the heat or the cold is more quickly conveyed downward, and therefore not allowed to accumulate on the surface. When the ground is covered with vegetation the whole of the sun's heat falls on the vegetable covering, and as none of it falls directly on the soil its temperature does not rise so high as that of land with no vegetable covering. The temperature of plants exposed to the sun does not rise so high as that of soil, because a portion of the sun's heat is lost in evaporation, and the heat cannot accumulate on the surface of the leaves as it does on the soil. Hence the essential difference between the climates of two countries, the one well covered with vegetation, the other not, lies in this, that the heat of the day is more equally distributed over the twenty-four hours in the former case, and there fore less intense during the warmest part of the day. But the effect of vegetation on the distribution of the temperature during the day is most markedly shown in the case of forests. Trees, like other bodies, are heated and cooled by radiation, but owing to their slow conducting power the times of the daily maximum and minimum temperature do not occur till some hours after the same phases of the temperature of the air. Again, the effects of radiation are in the case of trees not chiefly confined to a surface stratum of air a very few feet in thickness, but as already remarked, are to a very large extent diffused through a stratum of air equalling, in thickness at least, the height of the trees. Hence the conserving influence of forests on climate, making the nights warmer and the days cooler, imparting, in short, to the climates of districts clad with trees something of the character of insular climates. Evaporation proceeds slowly from the damp soil usually found beneath trees, since it is more or less screened from the sun. Since, however, the air under the trees is little agitated or put in circulation by the wind, the vapour arising from the soil is mostly left to accumulate among the trees, and hence it is probable that forests diminish the evaporation, but increase the humidity, of climates within their influence. The humidity of forests is further increased by the circumstance that when rain falls less of it passes immediately along the surface into streams and rivers; a considerable portion is at once taken up by the leaves of the trees and percolates the soil, owing to its greater friability in woods, to the roots of the trees, whence it is drawn up to the leaves and there evaporated, thus adding to the humidity of the atmosphere. Much has been done by Dr Marsh and others in elucidation of the influence on climate of forests and the denudation of trees, in so far as that can be done by the varying depths of lakes and rivers and other noninstrumental observations. Little comparatively has been done anywhere in the examination of the great practical question of the influence of forests on climate, by means of carefully devised and conducted observations made with thermometers, the evaporating dish, or the rain gauge. The most extensive inquiry on the subject yet set on foot. has been for some years .conducted in the forests of Bavaria under the direction of Professor Ebermeyer, and a like inquiry was begun in Germany in 1875,-the more important-results being that during the day, particularly in the warm months, the temperature in the forest is considerably lower than outside in the open country, there being at the same time a slow but steady outflow of air from the forest; and that during the night the temperature in the forest is higher, while there is an inflow of air from the open country into the forest. The mean annual temperature in the forest increases from the surface of the ground to the tops of the trees (where it is observed to approximate to what is observed in the open country), a result evidently due to the facility of descent to the surface of the cold air produced by terrestrial radiation, and to the obstruction offered by the trees to the solar influence at the surface. The mean annual temperature of the woodland soil from the surface to a depth of 4 feet is from 2° to 3° lower than that of the open country. A series of observations was begun at Carnwath, Lanarkshire, in 1873, at two stations, one outside a wood, and the other inside the wood in a small grass plot of about 50 feet diameter clear of trees. From these valuable results have been obtained relative to the differences in the daily march of temperature and the different rates of humidity, the most important being the substantial agreement of the mean annual temperature of the two places. The estab lishment of a station, with underground thermometers, which it is proposed to erect under the shade of the trees close to the station in the cleared space, will furnish data which will not only throw new light on the questions raised in this inquiry, but also on the movements and viscosity of the air and solar and terrestrial radiation. When the sun's rays fall on water they are not as in the case of land arrested at the surface, but penetrate to a considerable depth, which, judging from observations made, by Sir Robert Christison on Loch Lomond, and from those made on board the "Challenger," is probably in clear water about 600 feet. Of all known substances water has the greatest specific heat, this being, as compared with that of the soil and rocks composing the earth's crust, in the proportion of about 4 to 1. Hence water is heated much more slowly by the sun's rays and cooled more slowly by nocturnal radiation than the land. It is owing to these two essential differences between land and water with respect to heat that climates come to be grouped into the three great classes of oceanic, insular, and continental climates. The maximum densities of fresh and salt water, which are respectively 39°1 and 26°-2 (when the sea-water is the average degree of saltness), mark an essential distinction between the effects of sheets of fresh and salt water on climate. The surface temperature of sea-water falls very slowly from 39°1 to 28°-4, its freezing point, because as it falls the temperature of the whole water through its depths must fall; whilst from 39°1 to 32° the surface temperature of fresh water falls rapidly because it is only the portion floating on the surface which requires to be cooled. If the bottom temperature of fresh water exceed 39°1 the cooling takes place also very slowly, since in this case the water through all its depth must be cooled down to 39°1 as well as that of the surface. The temperature at the greatest depths of Loch Lomond, which is practically constant at all seasons, is not 47°8, the mean annual temperature of that part of Scotland, but 42°, which happens to be the mean temperature of the cold half of the year, or that half of the year when terrestrial radiation is the ruling element of the temperature. Thus, then, there is an immense volume of water at the bottom of this lake at a constant temperature 5°8 |