ANNIVERSARY ADDRESS OF THE PRESIDENT. xlix 



exposed ; the surface, to a considerable depth, being composed of clay, 

 sand, gravel and bonlders. These, over great tracts, are the detrital 

 matter that was accumulated on the then sea-bottom, during the glacial 

 period, the period of the northern drift. Where there are elevated 

 plateaux of these incoherent materials, the ground, during the exces- 

 sive heat and di'ought of summer, splits into vast cracks, which often 

 reach a great depth. These, in winter, are filled by accumulations of 

 snow and ice ; the thaw of the spring loosens the earthy matter, and a 

 grdley is formed, which mdens as it approaches the steep sides of the 

 plateaux, and in the course of a few seasons becomes a broad and deep 

 ravine, through which melted snow, mud and sand, and occasional 

 blocks and boulders, are transported into an adjacent river. These 

 ravines are of such frequent occurrence over large tracts of countiy, 

 that the quantity of matter carried into the streams must be enormous ; 

 this is afterwards transported to lower levels, or to the distant embou- 

 chures of the larger rivers, to form the rapidly increasing delta of the 

 Volga, or to silt up the Sea of Azof by the settlements from the muddy 

 waters of the Don. In the spring, large portions of the surface in 

 Russia are covered by water, from the melting of the snow, the higher 

 lands emerging hke isles or promontories ; "and when it is considered," 

 says Sir R. Murchison, " that such enormous volumes of water have 

 for ages flowed off to the sea through deposits, for the most part in- 

 coherent, we can well account for the increase of the deltas within the 

 historic period, at the mouths of all the chief or south-flowing rivers. 

 So great indeed must have been the mcrement of mxatter in the Cas- 

 pian, the Black Sea, and the Sea of Azof, that we must not be sur- 

 prised to find very essential distinctions between the features of the 

 present lands near the mouths of such rivers, and those which pre- 

 vailed during the earlier days of their occupancy by man. Thus, 

 freshwater shells common in the Volga have been found at about 300 

 feet below the city of Astrakhan, which is built upon the mud of that 

 river. By its daily-increasing delta, the Caspian is constantly en- 

 croached upon and diminished in area, the shallow water already ex- 

 tending to 40 and 50 miles south of the present embouchure*." 



It is interesting thus to trace the progress of change which the soHd 

 materials of the globe are destined to undergo, in that vast cycle of 

 decay and renovation which we know from irresistible evidence to have 

 been in progress during all geological periods, and which, if we are to 

 speculate on the future by what we have learned by the past, and by 

 what is going on under our own observation, is likely to continue. 

 Granite pinnacles, upheaved in Scandinavia, werein distant ages split and 

 shivered into fragments by the expansive power of freezing water ; and 

 these fragments, collected in moraines, were pushed along by the down- 

 ward movements of glaciers, and at length reached the sea of the glacial 

 period ; at a time when Central Russia was submerged, as we know 

 from very clear proofs, to a depth of at least a thousand feetf . By 

 the transportmg powers of water and ice, these fragments of Scan- 

 dinavian rocks were spread over the sea-bottom, hundreds of miles 



* Murchison's Russia, p. 572. 



f See my Anniversary Address of 1846, p. 60, 



