440 
The Hon. Mr. Strangways on the 
partly of chemical, partly of mechanical origin. In great floods, 
the quantity of water would be encreased and take up more lime, 
which it would deposit as it lowered by evaporation. Hence the 
great purity of this limestone and its fitness for burning into lime. 
The whole valley from Skvoritza, down to Poudost, or even 
beyond those two places, seems as if it might formerly have been a 
lake, which by the raising of its bed had run out towards Gatchina. 
The next important member of the post-diluvian formations 
occurring in this country are the great bogs, which are of vast 
extent, but in general of no great depth. They exactly resemble 
those in England, except that there is less mountain peat, most 
being of the coarser kinds usually found in vallies, and that they 
are more covered with wood. The firs, birch, and alder, and 
sometimes aspen, arrive at various heights according to the wetness 
or dryness of the bogs. Some, as those near Shulcova and Garlina, 
are so wet as to resemble a half liquid black paste, scarcely supporting 
even the common mosses from which it derives its origin. Many 
are absolutely impassable before the middle of winter. The dried 
bogs support a kind of coarse grass and most of the herbaceous 
plants peculiar to woods. 
It is not yet used for firing, but some English farmers have 
proposed it as a good material for burning bricks. Of late some 
attempts have been made at draining. 
The marsh land or alluvia formed by earthy depositions at the 
mouths or on the banks of rivers, lakes, &c. has already been 
noticed in the general description. It exists only on the shores of 
the gulf and in the mouth of the Neva. 
The sand thrown up by the sea may be noticed in this place, 
because it covers, at a small depth, the blue clay which may be 
seen here and there on the Oranienbaum shore. Many substances 
are dug up in the alluvium, coated with phosphate of iron. 
