324 ARCTIC SEA DEPOSITS ON THE DWINA AND THE YAGA. 
ferent and considerable altitudes. Whilst, therefore, we specially invite the atten- 
tion of geologists to the grandeur and peculiarity of this former internal sea, we 
think that its diminution to the size of the present Caspian and Aral seas, is 
mainly due to oscillations of its former bottom. The eruptive rocks which range 
along the Crimsea, the Caucasus and the Balkhan of Khwarezm, are fortunately 
at hand to explain, that as igneous matter in various forms has sought an issue at 
many points in those contiguous mountains, partially raising up sedimentary depo- 
sits, and changing their mineral aspect and condition ; so probably have internal, 
widely acting expansive forces, derived from the same deep-seated source, heaved 
up, in broad horizontal masses, to the different levels at which we now find them, 
the beds of the former great Caspian Sea. Such elevations would very naturally, 
we contend, be accompanied by adjacent depressions, and thus we would explain 
the low position of the Caspian Sea, and such portions of land around it, as are 
admitted by all observers to lie beneath the surface of the ocean. 
Lastly, by the tint upon our Map (1 0 f ) , which extends over the lower steppes, we 
merely seek to indicate a period, when the great and earlier Caspian had, by the 
elevation of its bottom, undergone a very notable diminution in size. Our con- 
clusion, that this intermediate condition — when such large tracts of our present dry 
lands were still covered by water, — was antecedent to our own sera, is, we may 
observe, strengthened by the absence of all traces of man or of his works in any of 
the most recent or lower, sandy deposits of these steppes. The remains of Mam- 
moths occur, indeed, in the sands and mud of the most recent of these desiccated 
Caspians with Mytili and shells adherent to them, showing by what races the ad- 
jacent lands were inhabited, when the waters of a Caspian covered the steppe of 
Astrakhan. On these terrestrial subjects, however, we shall not now dilate, though 
in the sequel we shall endeavour to explain the nature of the agency by which all 
these changes of land and water were brought about, and to indicate how the same 
causes, operating with much less intensity than in the preceding epochs, have 
produced comparatively small relative oscillations only within the histone age. 
Northern extension of a former Caspian. — M. Jasikoff has just communicated 
to us the interesting fact of the extension of Aralo-Caspian deposits considerably 
to the north of the limits with which we were acquainted. The most southern 
of these masses occurs in the low steppe on the left bank of the Volga, opposite 
