GEOLOGY 
formed at a much greater rate than any other limestone, and it is fully 
550 feet in thickness on the eastern side of England. 
Another phase of the terrestrial undulations finally reached Britain 
soon after the Magnesian Limestone had been formed. It would seem, 
judging by the evidence, that this undulation at first took the form of a 
local upheaval, sufficient in amount to elevate the lately-formed rocks into 
land; and it endured long enough to permit of a certain amount of 
waste and subsequent removal of the strata. 
(f) Then came another phase of the undulation, the effect of 
which appears to have been to further elevate the land—perhaps only to 
a small vertical extent—over a large area of western Europe. The sea 
margin, in an easterly direction at any rate, had now receded several 
hundreds of miles ; and we find instead of marine conditions, one or 
more great and shallow inland lakes, the strata formed in which show 
unmistakable evidence of a return of the desert conditions which had 
characterized the period before that of the Magnesian Limestone. The 
Cumberland lake received its waters, in small quantities at a time, from 
the adjacent mountain areas, some of which may have coincided with 
part of the present southern uplands of Scotland. There were certainly 
hills near where Moffat is now, and so there were in Galloway. Criffel 
is known to have formed part of an upland area at this time, for we 
have the old screes and wady deposits of this period left, even yet, in many 
places in that part of Galloway. This lake must have been comparable, 
in many respects, to the Salt Lake of to-day, and to many others of the 
same type as those existing in central Asia. It certainly extended eastward 
from Cumberland, past Middlesborough; and the same lake, or others of 
the same kind contemporaneous with it, existed in North Germany, and 
even Russia. Westward, it extended at least as far as the north of 
Ireland. It had no outlet, and the whole of the water carried into it by 
the few streams by which it was fed was dissipated by evaporation. 
Hence the various substances carried in solution into the lakes gradually 
accumulated, and eventually separated out in the crystalline form, when 
their respective points of saturation were reached. Amongst these sub- 
stances were carbonate of iron (subsequently consolidating as hematite) 
carbonate of magnesia, sulphate of lime (which consolidated as gypsum) 
chloride of sodium (common salt) and other compounds of lesser im- 
portance in the present connection. It is to this episode that we owe 
our chief deposits of hematite and manganese ; and it is likewise to the 
infiltrations from the bottom of this old lake that we owe the widespread 
staining of Carboniferous and older rocks of Cumberland, and also the 
conversion of many of the limestones of that county into dolomite. The 
rocks formed under the conditions described are the Bunter Marl, which 
is about 250 feet thick on the average. 
(g) After a long time the lake gradually became shallower, and 
instead of deposits of clay, beds of sand, alternating with beds of marl, 
were formed. This sand, afterwards consolidated into the sandstone 
which is known to us as the Corby Sandstone, St. Bees Sandstone, or 
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