l and southern Europe.

No definite conclusions can be drawn from the fossils as to the climatic
peculiarities of the earth in Cambrian times. The red rocks may in some
cases suggest desert conditions; and there is good reason to suppose
that in what are now Norway and China a glacial cold prevailed early in
the period.

Considerable variations occur in the thickness of Cambrian deposits,
which may generally be explained by the greater rapidity of deposition
in some areas than in others. Nothing could be more striking than the
difference between the thicknesses in western and eastern Europe; in
Brittany the deposits are over 24,000 ft. thick, in Wales at least
12,000 ft., in western England they are only 3000 ft., and in northern
Scotland 2000 ft., while no farther east than Scandinavia the complete
Cambrian succession is only about 400 ft. thick. Again, in North
America, the greatest thicknesses are found along the mountainous
regions on the west and on the east--reaching 12,000 ft. in the latter
and probably nearly 40,000 ft. in the former (in British
Columbia)--while over the interior of the continent it is seldom more
than 1000 ft. thick.

Any attempt to picture the geographical conditions of the Cambrian
period must of necessity be very imperfect. It was pointed out by
Barrande that early in Palaeozoic Europe there appeared two marine
provinces--a northern one extending from Russia to the British Isles
through Scandinavia and northern Germany, and a southern one comprising
France, Bohemia, the Iberian peninsula and Sardinia. It is assumed that
some kind of land barrier separated these two provinces. Further, there
is a marked likeness between the Cambrian of western Europe and eastern
America; many fossils of this period are common to Britain, Sweden and
eastern Canada; therefore it is likely that a north Atlantic basin
existed. Prof. Kayser suggests that there was also a Pacific basin more
extensive than at present; this is borne out by the similarity between
the Cambrian faunas of China, Siberia and Argentina. The same author
postulates an Arctic continent, bordering upon northern Europe,
Greenland and North America; an African-Brazilian continent across the
present south Atlantic, and a marine communication between Australia and
India, where the faunas have much in common.

REFERENCES.--The literature devoted to the Cambrian period is very
voluminous, important contributions having been made by A. Sedgwi