Chapter VII: The Atmosphere

At the present time we divide the study of the atmosphere into the sciences of meteorology, devoted to the investigation of individual and local atmospheric phenomena, and climatology, devoted to the investigation of the geographical distribution of weather conditions throughout the world as observed during long periods of time. We may make the same arbitrary division in dealing with the theories current in the twelfth and thirteenth centuries. Meteorology and climatology, however, merge into each other. Some understanding of one is absolutely essential to an understanding of the other, and hence we must take certain meteorological theories into consideration before attempting to deal with the more truly geographic subject of climatology.

_METEOROLOGY_

Probably the most complete and satisfactory extant treatment of meteorology from our period is to be found in the writings of William of Conches, whose interest in physics and in the natural sciences led him to study carefully the views of Seneca and also to express at great length opinions of his own about the atmosphere.[730]

COMPOSITION OF THE ATMOSPHERE

In the first place, William had very definite ideas concerning the composition of the air. The aerial and aqueous spheres, he said, act as intermediaries between the spheres of fire and earth.[731] The qualities of the two latter are opposite; but the atmosphere partakes more or less of the qualities of each, for neither sphere is made up exclusively of one element. William was an atomist: he thought that matter is composed of minute atoms and that each atom is the smallest conceivable particle of one of the four elements.[732] He explained that the atmosphere, which extends up as far as the moon’s orbit, contains in addition to the aerial atoms a certain number of aqueous particles in its lower levels and of fiery atoms higher up. Hence its density and humidity decrease progressively from the earth’s surface upward; the higher air is clear and lucid, the abode of good demons or angels, messengers of God to man, whereas the lower air is full of clouds and constitutes the abode of evil spirits.[733]

These parts of the atmosphere formed two out of five concentric regions into which William divided the entire universe.[734]

TEMPERATURE

With much acuteness of observation, William recognized the fact that the sun’s influence on the denser air of low altitudes is far more potent than it is on the rarer strata above.[735] Though heat comes from the sun, he said, it is not apparent until it becomes mingled with humidity. In valleys the air, lying stagnant and damp, is easily heated, whereas the dry upper levels remain cold even though the sun’s warmth passes through them. The presence of this coldness explains why snow is found on the summits of the highest mountains, for the belief that mountain snow is due to cold north winds William branded as false, observing that snow often occurs on the south as well as on the north sides of the peaks. Robert Grosseteste also held that the air at high altitudes is much colder than it is near the surface.[736] This, he said, was because the heating effect of the sun’s rays is inoperative on account of the transparency of the medium. At the surface heating takes place as a result of reflection and condensation of the solar rays.[737] The cold air at high levels explains the origin of perpetual snow on mountain tops. Hail is generated in these strata, rain at lower levels. Robert cited as proof of this the fact that birds of prey fly high in summer to cool off and that cranes and many other birds descend into the valleys to escape the icy chill but fly up the mountain sides to avoid the heat.[738]

UPPER LEVELS OF THE ATMOSPHERE

In contrast with these opinions of William of Conches and Robert Grosseteste, which were based apparently on more or less direct observation, we find echoes in our period of a doctrine that had its roots in classical mythology—the doctrine that above a certain height on mountain peaks the air is undisturbed by wind and unsullied by clouds.[739] Hermann the Dalmatian hints at this in his _Liber de essentiis_. In the course of a discussion of the dimensions of the habitable area of the earth’s surface that had probably been suggested by the reading of Arabic works he explains that the living offspring of the earth require for the maintenance of life a certain heavy, “greasy” terrestrial vapor which, “as Aristotle determined from the height of Olympus, does not rise more than sixteen stades above the earth’s surface. Here consequently would seem to be the upper limit of our habitable zone. Possibly this might be measured by means of the rainbow, which, according to the description of Hipparchus, reaches from the clouds themselves down to the surface of the earth. But since Hipparchus’ description is not accurate nor is the figure of the rainbow a semicircle, we leave the matter for whosoever may wish to prove it.”[740] Peter Alphonsi, who was also influenced by Moslem thought, placed the upper limit of the clouds at sixteen miles,[741] a figure which may have been derived from the same origin as Hermann’s sixteen stades. Peter Comestor inserted in his _Historia scholastica_ some observations in regard to the tranquillity of the summit of Mount Olympus and the physiological effects of the rarity of the atmosphere.[742] So quiet and untroubled by winds is this peak that letters written there in the dust remain legible for a year. The air is too thin even to support the life of birds, and several philosophers who climbed the mountain would have been unable to remain on top if they had not held to their faces sponges soaked with water and in this way made it possible to breathe by attracting denser air to their nostrils.[743]

CLOUDS

In this connection a puzzling question seems to have occurred to William of Conches. If the general rule holds that the atmosphere is rarer higher up than on the earth’s surface, how then does it happen that the upper air so often becomes dense in the form of clouds? To this William gave the correct answer,[744] that clouds are not composed of air of greater density than the surrounding parts of the atmosphere, but that water vapor arising from below is turned into clouds by the cold. True as it may be, this idea does not fit in very well with William’s theory of the coldness of the higher altitudes. First he maintains that one of the main reasons why the upper air is cold is because it lacks dampness; then he goes on to explain that dampness rising to a great elevation is converted by the cold into clouds. Though there is no direct contradiction of two statements here, one cannot but sense inconsistency and looseness of thought of a sort that pervades all medieval natural science, though William of Conches on the whole was rather less illogical and less inconsistent than most of his contemporaries.

Much the same explanation of the effects of cold on the condensation of water vapor is found in the _Dialogus_ of Peter Alphonsi,[745] where it is shown that the sun draws a damp vapor from the sea and a dry humor from the land. Out of a combination of these, clouds are formed which rise until they reach a height of about sixteen miles. Here, coming in contact with strata of cold air, they are prevented from ascending any higher, and the damp vapor may be precipitated in the form of rain.

PRECIPITATION

William of Conches also endeavored to explain rainfall.[746] This phenomenon may result, he said, from various causes: either from the conversion into drops of water of dense vapors arising from the earth, from the actual transformation of air into water through the influence of cold, from the tumbling back to earth of some of the water which the sun raises to itself for its own nourishment,[747] or, finally, from water swept up by the winds off the surface of streams, lakes, and swamps. That the last was possible he believed to be demonstrated by the fact that frogs sometimes fall with raindrops![748]

Theodoric of Chartres gives a clear statement[749] of the theory of evaporation, condensation, and precipitation in terms that sound almost modern. Heat, he says, causes water to ascend into the atmosphere in minute drops which form clouds. If the heat increases, these droplets turn to pure air; if it diminishes, they coalesce into rain. The most minute drops are constricted by a cold wind into snow; when the drops are large they are converted into hail by the same agency.[750]

Topographic influences on precipitation were partially understood by Giraldus Cambrensis, who believed that the influence of land—particularly hilly land—frequently tends to change the vapors of the air into mists and clouds, or rain and snow.[751] In the seas off Ireland, for instance, water is attracted into the atmosphere in immense quantities; the temperature being equable, the water is neither consumed by an excess of heat nor turned to snow by an excess of cold but is altered into rain, a process greatly facilitated by the presence of many mountains in Ireland.

FLOODS; THE DELUGE

An excess of rainfall results in floods. William of Conches believed that under normal conditions the warmth of summer counteracts the excessive dampness of winter but that a long series of cool, damp summers will end in floods and, conversely, a series of hot, dry summers will end in droughts. But, however many local floods there may be, only one _diluvium_, or deluge, is possible.[752]

Whence came the waters of the Deluge? This was a question which puzzled some of the commentators on Scripture during the Middle Ages. Adelard, though he did not believe it himself, cited a theory that the purpose of the waters above the firmament was to furnish these waters.[753] Peter Comestor,[754] followed by Gervase of Tilbury,[755] said that they came partly from the bowels of the earth and partly from the air above and that they rose higher than the tops of the mountains of today,[756] to the level to which the vapors of burnt offerings ascend. Gervase also spoke of a curious theory that there may have been no rain in Paradise nor anywhere on the earth until the time of the Deluge.[757] The vegetation in the Garden was watered in these early days by the heavenly dew. The argument that no rain fell until the Deluge was based, he said, on the words of God to Noah: “I will no more curse the earth for the sake of men; ... seedtime and harvest, cold and heat, summer and winter, night and day shall not cease” (Gen. viii, 21–22). Gervase adds: “Perhaps the four seasons were not yet fully distinguished one from the other, since not until the time of the Deluge were the waters gathered into clouds.”[758] According to the _Liber divinorum operum_ of Hildegard the temperature was far hotter before the Deluge than it has been since, and “the men of that time possessed great bodily strength in order that they might endure this heat. The Deluge reduced the temperature, and men since have been weaker” (Thorndike).[759]

WINDS

The winds interested the men of the twelfth and thirteenth centuries even more than rainfall. Popular notions of winds, rain, and storms as manifestations of magical powers or evil spirits,[760] though universally believed among the unlearned, were not given serious consideration by the majority of scholars. Isidore, Bede, Raban Maur, and those who copied from them during our period—the author of the _De imagine mundi_[761] and Gervase of Tilbury in his _Otia imperialia_—defined wind as air in a disturbed and agitated condition,[762] Adelard of Bath said it was dense air moving in a particular direction,[763] and William of Conches used Seneca’s definition, “Wind is air flowing one way.”[764]

Hildegard of Bingen made the winds play a supremely important part in the dynamics and physics of the universe. To the winds she ascribed the movement of the firmament from east to west and of the planets from west to east.[765] Were it not for the winds, she said, the fires of the south, the waters of the west, the shadows of the north would burst forth over the earth. The four winds are the wings of God’s power; were they to move forward at once all the elements would be confounded and split asunder, and they would shake the sea and dry up its waters.[766] As the body of man is held together by the soul, so the whole firmament is kept intact by the winds lest it be corrupted; and the winds are invisible like the soul, which comes from the mystery of God[767] (see Fig. 5, p. 149).

What causes the wind? William of Conches made one of the most elaborate attempts in many centuries to answer this,[768] for, though borrowing largely from Seneca, he added some significant observations of his own. In the first place he argued that local winds are produced by various local causes, as, for instance, when air enters a cavern, on account of its _labilitas_, or fluidity, it tends to force out the air already there and thus to make a commotion which generates wind. We may be allowed to suppose here that William has in mind a cavern with two entrances, for it is difficult to understand how such an effect could be produced in a cavern with only one. Similarly, William thought that waters entering the hollows of the earth tend to force out the vapors therein contained and thus to produce blasts and even earthquakes. A damp vapor in rising might cause a wind to blow on account of the removal of its weight (_ex ponderatione sua_). William borrowed the idea that winds may result from the destruction and flattening out of clouds directly from the ἐκνέφτα, or “cloud breezes,” of Aristotle and Seneca. Adelard of Bath also attributed the origin of certain winds to local exhalations of vapors off the surface of land and water. “Marshes and valleys give up a great deal of dense air, which in the natural course of things rises upward; further, when they are loosened, they give back to its natural position much moisture of water which they had previously held imprisoned; add to this that I do not exclude from my statement the actual air which is the content of earth” (Gollancz’s translation).[769]

_Atmospheric Circulation_

The most original theory of the winds was not any of those which attempted to account for purely local breezes but an explanation propounded by William of Conches of the circulation of the atmosphere as a whole. Unlike our modern conceptions of atmospheric circulation based on the observation of facts, William’s ingenious theory seems to have been the product of his own vivid imagination. It was founded on a persistent idea, dating back to classical times, that disturbances in the water can produce currents of air. Gervase of Tilbury, for example, states in so many words that “mountains and water cause winds” and that the swift-flowing Rhone makes the _mistral_ that blows over Provence and Dauphiny.[770] William of Conches[771] believed that there are two ocean currents trending east and west out of the equatorial ocean. Each of these was supposed to divide in two at the extremities of our _oikoumene_, making four currents which collide at the North and South Poles in the ocean perpendicular to the equatorial ring (Amphitrites). The cardinal winds are generated at four points, at the two junctions of the oceans where the currents divide and at the poles where they collide. The western division gives rise to Zephyr, the eastern to Eurus, the collision at the North Pole to Boreas, and the one at the South Pole to Auster. It may happen, however, that one of the currents will on occasion flow more strongly than its opponent and will push the point of collision beyond the pole. This displacement of the point of collision explains the blowing of the collateral winds. Absurd as it may be in itself, this theory is of interest to us mainly because it shows that William understood that a broad system of atmospheric circulation is possible and assigned to it, as well as to local breezes, a purely physical cause. Curiously enough, it is the exact reverse of our modern conception of the usual relation existing between atmospheric and ocean currents, for now we understand that the winds are more effective as the cause of the ocean currents than vice versa.

William also maintained, as we shall see later,[772] that the tides are produced by the impact of ocean currents. Why then, it was asked, if the tides are of daily, periodic occurrence, do not the winds, which he tells us result from the same cause, show a similar periodicity? To this William replied[773] that the winds in fact do show such regularity but that it is not apparent to us for two reasons: in the first place, wind produced by these causes does not always reach the part of the earth where we happen to be; and, secondly, the resulting wind may blow at such a high altitude as not to be noticed by men on the ground—an observation now well known to be true.

_Names of the Winds_

Classical names for the winds were almost universally employed. The distinction between cardinal and collateral which was made by William of Conches goes back to the Greeks,[774] who had conceived of four cardinal and four, six, seven, or eight collateral winds. Seneca’s[775] rose of twelve winds, the idea of which in its essentials had been derived from Posidonius, Timosthenes, and, ultimately, from Aristotle, was adopted by Isidore, who passed it on to the Middle Ages, though terrible confusion (which, happily, it is not necessary for us to unravel) reigned at all times regarding the names employed to designate its elements.[776] In addition to the classical terms, our modern names were already familiar. In the Ghent manuscript of Lambert of St. Omer’s _Liber floridus_[777] there is a diagram in which the winds are called “ost-ost,” “sud-ost,” “sud-sud,” “sud-west,” “west-west,” “nord-west,” “nord-nord,” and “nord-ost.” This terminology was used in the time of Charlemagne[778] and is probably of Anglo-Saxon origin,[779] although it has been suggested that the terms are corruptions of Latin words—“ost” from “Augustus;” “ovest,” or “west,” from “ob est;” “nord” from “novus arctus,” etc.[780]

_Qualities of the Winds_

To the various winds classical and medieval writers liked to attribute qualities—or, at any rate, descriptive adjectives, “cold” or “hot,” “dry” or “damp,” “stormy” or “calm,” and the like—but there was little enough uniformity in making these distinctions. Some writers of our period seem to have been content merely to repeat what had been said in classical times; others, like William of Conches or Giraldus Cambrensis, showed more independence. Boreas was probably universally regarded as cold and Auster as hot, but beyond this we cannot generalize.[781] William of Conches[782] conceived of the winds as partaking of the qualities of the regions over which they blow: Auster, coming from the South Pole and hence originally frigid like Boreas, in its passage across the torrid, equatorial zone becomes hot and dry—an observation which may perhaps be founded on some knowledge of the _sirocco_ of the Mediterranean. On the other hand, Giraldus Cambrensis, undoubtedly from personal acquaintance with the water-laden south and southwest gales of the British Isles, calls Auster damp and rainy in winter. Similarly Giraldus breaks with classical tradition when he speaks of the east wind, or Eurus, as pure and clear, a bringer of fair summer weather, strikingly different from Zephyr, wet and cloudy from the sea.[783]

_Local Winds_

We find occasional descriptions—some of them from personal observation, no doubt—of winds peculiar to particular parts of the world. Gervase of Tilbury, as we have seen, tells of very violent blasts in the Rhone valley,[784] supposedly generated by the current of the river in a region now famed for the furious _mistral_ that sweeps across Dauphiny and Provence from the north. In another connection[785] he tells of a valley in the Kingdom of Arles, once so shut in by precipitous mountains that no winds at all entered it and that it consequently was sterile and useless. In the time of Charlemagne, however, Caesarius, the archbishop of Arles, filled his glove with sea breezes and let them forth in the valley; thus originated a wind known as _pontianum_, which wrought an immediate change in the character of the place and caused it henceforth to become fertile and healthy. This wind was doubtless the breeze now called _pontias_ that blows at Nyons in the Department of the Drôme; but as to its miraculous origin Gervase is merely repeating one of many popular medieval stories.[786]

William of Tyre[787] describes in vivid terms the _simoom_ of the Arabian desert and how men have to lie flat on the ground at the time of its passing: equal to a storm at sea, it sweeps down upon the traveler waves of sand as huge as those of the sea and causes grave danger to persons who would cross the desert.

_CLIMATOLOGY_

The most important factor in determining the atmospheric climate of any given region is the amount of sunlight and heat received. This, in turn, depends largely on geographical latitude. As we have already discussed the broad climatic divisions of the earth’s surface in zones, it remains here for us to deal merely with what was known of climatic conditions within the _oikoumene_.

HOT AND COLD CLIMATES

Climatic differences between northerly and southerly latitudes were well understood. Classical writers had told of the coldness of the regions beyond Thule, and in the _De imagine mundi_[788] we read that in those parts the sea is frozen and perpetual cold prevails. An interpolation into Solinus’ _Collectanea rerum memorabilium_ dating perhaps from our period contains a vivid and possibly exaggerated description of the cold of Iceland: “These people also are good Christians, but in winter they dare not leave their underground holes on account of the terrible cold. For if they go out they are smitten by such terrible cold that they lose their color like lepers and swell up. If by chance they blow their nose, it comes off and they throw it away” (Nansen’s translation).[789] Giraldus Cambrensis praises the temperate climate of Ireland, placed between the torrid warmth of Spain and the rigors of Iceland;[790] and the chroniclers and historians of the Crusades give evidence of first-hand knowledge of the terrific summer heats in the Holy Land.[791] Ambroise says, for example:

“Ca c’est entur la seint Johan
Que la chalur tote rien seche
En la terre, tele est sa teche.”[792]

Benjamin of Tudela’s extensive travels made him familiar with countries of widely different climate. The peculiarities of some of these he notes briefly. Writing of Russia, for example, he remarks that “no one issues forth from his house in winter time on account of the cold. People are to be found there who have lost the tips of their noses by reason of the frost” (Adler’s translation).[793] Similarly it was his belief that in Khulam (or Quilon) in southern India no one left his home all through the summer on account of the sun.[794] A hint of the intensity of the Mesopotamian summer is given in a description of a hospital in Baghdad, which Benjamin had perhaps seen, “where they keep charge of the demented persons who have become insane through the great heat ... and they chain each of them with iron chains until their reason becomes restored to them in the winter time” (Adler’s translation).[795]

DISTRIBUTION OF CLIMATES

William of Conches, in his usual manner, tried to generalize on climates. He said that our habitable portion of the earth’s surface is not of an even temperature throughout. The parts nearest the torrid zone, Ethiopia and Libya, are hot and dry; the northern parts near the frigid zone are cold and damp. Furthermore, though for us it is less easy to see exactly why, the West is cold and dry, and the East warm and damp. The symmetry of the system is perfect: climates vary in a direct ratio with distance, or, as William puts it, “Aequaliter vero distans, aequaliter est temperata.”[796]

CLIMATIC DIFFERENCES BETWEEN EAST AND WEST

Men were not so well agreed in the Middle Ages regarding differences of climate between East and West as regarding those between North and South. Bartholomew Anglicus[797] believed the West to be cold and damp and the East hot and dry, an opinion unlike that of William of Conches in that it may well have been based on actual observation rather than on theory. Giraldus Cambrensis in the _Topographia Hiberniae_ gives a long discourse[798] on climatic and other differences between the Orient and Occident, in which his main contention is that, though the air is clearer, finer, and more “subtle” in the East, the stormy and damp climates of the West are better for the health. The true climate of the Orient—that is of the Levant—had been made known to the Occidental world through the Crusaders, who often dwelt with insistence on its disagreeable and injurious qualities, especially the heat, dust, and thirst of the Syrian summer, which dried cisterns and carried disease and death in its train. In the East, Giraldus says, everything threatens the traveler, and he writes a word of warning against doing many of those very things which the modern wanderer in the Levant knows to be imprudent: such as going uncovered, sitting on rocks, or overeating.[799]

TOPOGRAPHIC INFLUENCES UPON CLIMATE

_The Sea_

During our period we find several descriptions of local climatic conditions and of variations due to topographic features like sea and mountains. A vivid impression of the wild marine weather of the North Atlantic off the coast of Ireland is given us in the narrative of St. Brandan’s wanderings. The saint and his companions were forced to remain three months on an island because of storms with furious gales, rain, and hail.[800] Giraldus Cambrensis[801] pictures the turbulent climate of Ireland, an isle surrounded by vast seas, unprotected and exposed to all the blasts. He was especially struck by the thick and rainy westerly gales, Zephyr and Corus, which bend over the trees in the seaward parts of the island. However violent the winds, Giraldus maintained that Ireland is the most temperate of all lands:[802] snow there is infrequent and when it comes lasts but a short while. Though cold weather accompanies all the winds, it never becomes too cold, and green grass grows in the pastures at all times of year. Yet so constant is the dampness, so prevalent the rain and clouds, that a clear day is rare indeed.

_Mountains_

William of Conches speaks in general terms of the influence of mountains on climate. We have seen how he recognized the fact that the tops of mountains are colder than the valleys below.[803] In another connection[804] he explained that places cut off from the north winds by mountains have dry, warm conditions and are good for winter residence, though less desirable in summer. The opposite is true of places on the north sides. Similarly, places exposed to the east are warm and damp with a pleasant autumn but bad spring weather, and the converse is true of places with a western exposure. This systematic arrangement is deduced from William’s fundamental and oversymmetrical conception of the various climatic characteristics of the cardinal points of the compass.

Gunther of Pairis, in his _Ligurinus_,[805] embellishes a description of the mountain ranges of Italy with an imaginative discourse on how they influence the climate: the Apennines temper the moist, summer heat of the south wind, and the crags of the Alps cut off the cold northerly gales of Boreas and Arctos. Giraldus Cambrensis says[806] that Ireland, like all other mountainous districts, produces an abundance of rain. In the _Itinerarium Kambriae_[807] he explains that the lake of Brecknock (Llangorse) in Wales is encircled north, west, and south by high mountains. The great range of Cader Arthur to the south, by cutting off the rays of the sun, renders the climate in the vicinity of the lake both pleasant and healthy. The valley of Ewyas, completely surrounded by mountains (now the Black Mountains), is constantly the resting place of clouds, strong gales, and rain, which make it, in Giraldus’ opinion, an extremely healthful locality.[808]

We cannot leave this subject without alluding again to the theoretical discussion of the influence of mountains on the climate of the polar regions that is found in that most interesting treatise of Robert Grosseteste, the _De natura locorum_. The bishop of Lincoln recognized the fact that insolation is greatly reduced in high latitudes owing to the obliquity of the sun’s rays and that the climate normally should be too cold to sustain life. He believed, however, that the presence of very high mountains, Rhipaean, Hyperborean, and others to which the authorities referred, might totally neutralize the effects of position in relation to the sun’s rays. “Some of these mountains,” he wrote,[809] “are smooth of surface, like the salt or rock hills that are found in many places, and others are in the nature of crystal, as divers authors and explorers testify, so that the reflection from them is good. As a result of this they are able to cause the rays all to converge and to produce a powerful effect. From these two accidental causes, that is from the smoothness of the mountains and from their concave shape, there is an intense heating of the air in certain regions around the pole. The great height of some of these mountains also cuts off the cold of the north, and thus certain localities may well be intensely hot.” On the other hand, Grosseteste had learned from Capella, Pliny, Solinus, and “many others who describe the regions of the world that in the Hyperborean Mountains next to the pole there are men who are called Hyperboreans from these mountains. And they enjoy the most temperate and healthy of climates and as a result live to such an age that they grow tired of life and without other cause throw themselves off of high rocks into the sea and die. The cause of this may be assigned to the form of the mountains beneath which they dwell, inasmuch as these mountains are smooth and of even surface, nor are they concave but are elongated (_oblongam_) and convex or of some other shape which does not concentrate the heat in those regions but on the contrary renders the climate temperate.”[810]

INFLUENCE OF CLIMATE ON MAN

In the literature of our period we find several observations about the influence of climate on man. Gervase of Tilbury[811] maintained that the character of the different European peoples varies with varying climatic conditions. “According to the diversities of the air the Romans are grave, the Greeks fickle and unreliable, the Africans sly and crafty, the Gauls fierce, and the English and Teutons powerful and robust.”

In another connection[812] he explains that the violent _mistral_ of the Rhone valley generates in this region men who are windy, empty-headed, inconsistent, and most unreliable in their promises. The supposedly mollifying influence of a warmer climate on the Lombards is hinted at by Otto of Freising.[813] Otto believed that these tribes gave up their ferocity on settling in Italy, where they adopted Italian customs, partly because they married Italian women but partly also because of the nature of the country and climate (_ex terris aerisve_). We have already seen how Giraldus Cambrensis stressed the healthy qualities of damp and humid Ireland in contrast with the disease-breeding Orient. Even the most delicate persons thrive in Ireland, he said, and though the Eastern air may endow men with keener wits and intelligence, the West gives them stronger bodies and a more martial spirit.[814]

CLIMATE OF ROME

If we may believe Otto of Freising[815] and Gunther of Pairis,[816] the climate of Rome was even more noxious and dangerous in the twelfth than in the nineteenth century. Otto tells us that Frederick Barbarossa’s army arrived in Rome in midsummer when the Dog Star was on high. It was a time when the ponds, caverns, and ruinous places around the city were exhaling poisonous vapors, and the air in the entire vicinity had become densely laden with pestilence and death. Gunther enlarges on this, giving a circumstantial, though probably fanciful, account of the effects of the terrible Roman summer on the German army, especially of the disease and malaria engendered by the climate and foul condition of the city.[817]