572 
ANNUAL WEAR AND TEAR OF THE SURFACE. 
to the fissured nature of the sides of the hills, and the wide mouths of these gulleys, 
that the great roads of Russia pass almost invariably over the very highest parts of 
the table-lands, where the “avrachs” are, comparatively speaking, small or rare. 
Instead of travelling along the banks of the great water-courses, as would be the 
case in western Europe, it has been found impossible to maintain roads along these 
lower levels, — first, from their being inundated during the spring season ; and, 
secondly, by the innumerable mouths of the ravines, which defy all the efforts of 
bridge-makers, and are for ever changing their courses and dimensions. 
In the mean time, though by unchecked natural processes, the finest plateaux 
of Russia should, in the lapse of ages, be levelled with the plains, yet has the 
geologist to thank these “ avrachs” for most of his best sections ; since it is gene- 
rally near their mouths, where the denudation has been deepest, that the parent- 
rock or true subsoil is laid bare. 
State of the Surface of Russia during the Spring Floods. — Increase of Deltas arid 
Formation of new Lands. — Mud Volcanoes. — Elevations of Land, &c. — The great 
amount of change which Russia has experienced, and is undergoing by the degradation 
of her perishable subsoil, is, as we have said, mainly due to an excessive climate. 
The enormous volume of water, by which large portions of her surface are still 
covered at every annual melting of the snows, can scarcely be imagined, except 
by those who have traversed (we may say sailed over) some of the central and 
southern countries in the spring season, when to the eye of the geologist the lands 
seem to be emerging, like isles and promontories, on all sides from beneath the 
waters. It is then that each broad valley is, for six weeks or more, in a condition 
similar to that which we can imagine to have been the state of England, France 
and other countries, when their streams, instead of occupying their present beds, 
were lake-rivers or estuaries of great width, wherein many of the old gravel and 
sand-banks of geologists were accumulated, and in which the bones of extinct 
mammals are found. 
The height of the waters during this annual inundation can, indeed, be exactly 
read off, wherever any great stream has rocky banks. In gorges we have occa- 
sionally noted the spring high-water mark as having been forty feet above the dry 
summer level ; and when it is considered, that such enormous volumes of water 
have, for ages, flowed off to the sea through deposits, for the most part incoherent, 
we can well account for the vast increase of the deltas, within the historic period, 
at the mouths of all the chief or south-flowing rivers. 
