The Sun.
London, England, 1864-09-15 00:00:00

enced in these latitudes, though not to such extreme oold as
that implied by the fauna of some of the glacial drift of
Scertland. Shells were procured at the extraordinary height
of 1,360 feet above the sea-level, and they demonstrate an
upheaval of the bed of the sea to that amount in the time of
living Testacea. A considerable part of what is called the
glacial epoch had already elapsed before the shelly strata in
question were deposited on Moel Tryfaen. The evidence
of a period of great cold in England and North America in
the times referred to is now so universally admitted by geo-
logists that I shall take it for granted in this address, and
briefly consider what may have been the probable causes of
the refrigeration of central Europe at the era in question.
One of these causes, first suggested eleven years ago by a
celebrated Swiss geologist, has not, I think, received the at-
tention which it well deserved. When I proposed, in 1833,
th© theory that alterations in physical geography might
have given rise to those revolutions in climate which the
earth's surface has experienced at Successive epochs, it was
objected by many that the signs of upheaval and depression
were too local to account for such general changes of tem-
perature. But the more we examine the monuments of the
ages which preceded the historical, the more decided become
the proofs of a general alteration in the position, depth, and
height of seas, continents, and mountain chains since the
commencement of the glacial period. The meteorologist also
has been learning of late that the quantity of ice and snow
in certain latitudes, depends not merely on the height of
mountain chains, but also on the distribution of the sur-
rounding sea and land even to considerable distances. M.
Escher von der Linth gave it has his opinion, in 1852, that
if it were true, as Hitter had suggested, that the great
African desert, or Sahara, was submerged within the modern
or post-tertiary period, that same submergence might ex-
plain away why the Alpine glaciers had attained so recently
those colossal dimensions which, reasoning on geological
data, Venetz and Charpentier had assigned to them. Since
Escher first threw out his hint, the fact that the Sahara was
really covered by the sea at no distant period has been con-
firmed by many new proofs. The distinguished Swiss geo-
logist himself has just returned from an exploring expedi-
tion through the eastern part of the Algerian desert, in
which he was accompanied.by M. Desor, of Neuchatel, and
Professor Martins, of Montpellier. The three experienced
observers satisfied themselves, during the last winter, that
the Sahara was under water during the period of the living
species of Testacea. The ancient sea appears once to have
stretched from the Gulf of Cebes, in Tunis, to the 'West
Coast of Africa, north of Senegambia, having a width of
several hundred (perhaps where greatest, according to Mr
Tristram, 800) miles. The high lands of Barbary, inclu-
ding Morocco, Algeria, and Tunis, must have been sepa-
rated at this period from the rest of Africa by a sea. All
that we have learnt from zoologists and botanists in regard
to the present fauna and flora of Barbary favours this hypo-
thesis, and seems at the same time to point to a former
connection of that country to Spain, Sicily, and South
Italy. In whatever direction, therefore, we look, we see
grounds for assuming that a map of Africa in the glacial
period would no more resemble our present maps of that
continent than Europe now resemble North America. If,
then, argues Escher, the Sahara was a sea in post-tertiary
timee, we may understand why the Alpine glaciers formerly
attained such gigantic dimension,, and why they have lett
moraines of such magnitude on the plans of Northern
Italy and the lower country of Switzerland. M, Denzier
172 a memoir on this subject, observes that the Fohn
(Sirocco) blew tempestuously at Algiers on the 17th of
July, 1841, and then crossing the Mediterranean, reached
Marseilles in six hours. In five mote hours it was at Geneva
and the Valais, throwing down e large extent of forest in
the latter district, while in the cantons of Zurich and the
Grisons it suddenly turned the leaves of many trees from
green to yellow. In a few hours new-mown grass was dried
and ready for the haystack ; fur although, in passing over
the Alpine snows, the cite coo absorbs much moisture, it is
far below the point of saturation when it reaches the sub-
alpine country to the north of the great chain. MM. Eicher
and Donzler have both of them observed on different occa-
sions that a thickness of one foot of snow has disappeared in
four hours during the prevalence of this wind. No wonder,
therefore, that the Fohn is much dreaded for the sudden
inundations which it sometimes causes. The snow line of
the Alps was seen by Mr Irscher, the astronomer, from his
observatory at Neuchatel, by aid of the telescope, to rise
sensibly every day while the wind was blowing. Its influ-
ence is by no means confined to the summer season, for in
the winter of 1852 it visited Zurich at Christmas, and in a
few days all the surrounding cour.try was stripped of its
snow, even in the shadiest places, and on the crests of high
ridges. It is well-known that the number of days during
which particular winds prevail, from year to year, varies
considerably. Between the years 1812 and 1820 the Fohn
was less felt in Switzerland than usual; and a hat was
the censequence ? All the glaciers during those eight or
nine years, increased in height, and crept down below their
former limits in their respective valleys. Many similar
examples might be cited for the sensitiveness of the ice to
slight variations of temperature, If such changes can be
experienced in less than a century, without any perceptible
modification in the rhysical geography of that part of
Asia, what mighty Effect may we not imagine the sub-
mergence of the Sahara to have produced in adding to
the size of the Alpine glaciers; If, between the year 1812
a-ed 1820, a mere diminution of the number of days dur•
ing which the sirocco blew could so much promote the
growth and onward movement of the ice, how much
greater a change would result from the total cessation of
the same wind F But this would give no idea of whit
Inuit have happened in the glacial period ; for we cannot
suppose the action of the south wind to have been sus-
pended ; it was not in abeyance, but its character was
entirely different, and of an opposite nature, under the
altered geographical conditions above contemplated. First,
instead of passing over a parched and scorching desert, be-
tween the twentieth and thirty fifth parallels of latitude, it
would plentifully absorb moisture from a sea many hun-
dreds of miles wide. Next, in its course over the Medi-
terranean, it would take up still more aqueous vapour; and
when, after complete saturation, it struck the Alps, it would
be driven up into the higher and more rarified regions of
the atmosphere. There the ariel current, as fast as it was
cooled, would discharge its aqueous burden in the form of
snow, so that the same wind which is now called " the
devourer of ice" would become its principal feeder. If we
thus embrace Escher's theory, as accounting in no
small degree for the vast size of the extinct glaciers
of Switzerland and Northern Italy, we are by no
meansdebarred from accepting at the same time Char-
pentier's suggestion, that the Alps in the glacial
period were 2,000 or 3,000 feet higher than they are
now, Such a difference in altitude may have been an
auxiliary cause of the extreme cold, and seems the more
probable now that we have obtained unequivocal proofs of
such great oscillations of level in Wales within the period
under consideration. We may also avail ourselves of
another source of refrigeration which may have coincided
in time with the submergence of the Sahara, namely, the
diversion of the Gulf Stream from its present course.
The shape of Europe and North America, or the bounda-
ries of sea and land, departed so widely in the glacial
period from those now established, that we cannot sup-
pose the Gulf Stream to have taken at that period its pre-
sent north-western course across the Atlantic. If it took
some other direction, the climate of the north of Scotland
would, according to the calculations of Mr Hopkins,
suffer a diminution in its average annual temperature of
12 deg. Fahr., while that of the Alps would lose 2 deg.
Fehr. A combination of all the conditions above enume-
rated would certainly be attended with so great a revo-
lution in climate as might go far to account for the ex-
cessive cold which was developed at so modern a period in
the earth's history. The more we study and comprehend
the geographical changes of the glacial period, and the mi-
grations of animals and plants to which it gave rise, the
higher our conceptions are raised of the duration of that
subdivision of time, which, though vast when measured by
the succession of events comprise] in it, was brief, if esti-
mated by the ordinary rules of geological classification,
Tho glacia' period was, in fact, a mere episode in one of the
great epochs of the earth's history; for the inhabitants 01
the lands and seas, before and after the grand development
of snow and ice, were nearly the same. As yet we have no
satisfactory proof that man existed in Europe or elsewhere
during the period of extreme cold ; but our investigations
on this head are still in their infancy. In an early portion
of the poet-glacial period it has been ascertained that man
flourished in Europe ; and in tracing
the signs of his exist-
ence, from the historical ages to those immediately ante-
cedent, and so backward into more ancient times, we gradu-
ally approach a dissimilar geographical state of things,
when the climate was colder, and when the configuration of
the surface departed considerably from that which now pre-
vails. Archaeologists are satisfied that in central Europe,
the age of bronze weapons preceded the Roman invasion of
Switzerland ; and prior to the Swiss lake-dwellings of the
bronze age were those in which stone weapons alone were
used. The Danish kitchen-middens seem to have been of
about the same date; but what M. Lartet has called the
reindeer period of the South of France was probably ante-
eor, and connected with a somewhat colder climate. Of still
higher antiquity was that age of ruder implements of stone
such as were buried in the fluviatile drift of Amiens and
Abbeville, and which were mingled in the Fame gravel with
the bones of extinct quadrupeds, such as the elephant,
rhinoceros, bear, tiger, and hyena. Between the present
era and that of those earliest vestages yet discovered of our
race, valleys havobeen deepened, the course of subterranean
rivers,which 0:lee flowed throughcaverns, has been changed,
and many species of wild quadrupeds have disappeared. The
bed of the sea, moreover, has in the same ages been lifted
up, in many places hundreds of feet above its former level,
ned the outlines of mar y a coast entirely altered. MM, de
Verneuil and Louis Lartet have recently:found near Madrid
. fossil teeth of the African elephant, in old valley drift, con-
taining flint implements of the same antique type es those
of Amiens and Abbeville. Proof of the same elephant
leaving inhabited Sicily in the post-Pliocene and probably
within the human period had previously b en brought to
light Icy Baron Anca, during his exploration of the bone
caves of Palermo. We have now therefore evidence of man
having co-existed in Europe with three species of elephant,
two of them extinct (namely, the mammoth and the-Elephas
that some
of
!Tyittruts), and a third the same as that which still survives
in Africa. As to the first of these—the mammoth--I am
aware
writersthousands
contend
yearsth that it
beforecouldu
o r
time,not h
have died
out manytens because
its flesh had been found preserved in ice, in Siberia, in so
fresh a stale us to serve as food for dugs, bearsland wolves;