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]