Geology of the Environs of Petersburg . 437 
hollowed out till the diluvian waters began to draw off and drag 
the slopes of what had been the bottom of the ocean. The heavy 
blocks had already settled, and the streams carried back with them 
only the softer materials. This accounts for the seeming incongruity 
in the direction of the diluvian currents ; just as a great wave of 
the sea will transport pebbles large and small in a great body in one 
direction ; then, retreating, drop the heavier and scoop channels in 
the lighter materials which it has itself just deposited, and in 
whatever is below them ; into some of which channels a few large 
pebbles fall back again. 
This also explains the remarkable circumstance of the existence 
of large deposits of diluvian gravel on the summits of insulated 
hills, as at Doudorof. The gravel has been equally deposited at 
first on the surface of the strata, by the great debacle; and as it 
draws off, certain portions of the solid strata with their new diluvian 
covering have been removed, and other portions of the same strata, 
insulated or connected, have been left with whatever was above 
them. I imagine the eddies, currents, back streams, and whirlpools 
of the diluvian waters to have had as much share in the shaping of 
the surface of our present earth, as any supposed difference of 
hardness between one portion of the same stratum and another. 
The fragments which remain to attest the solidity of many vast 
masses of strata which have been broken up and carried away r 
seem to countenance this supposition.* 
* This part of Russia appears to be as poor in the remains of quadrupeds usually found 
rolled in diluvian gravel, as other parts of the same country are rich in them. 
I can only mention a scull said to be that of a rhinoceros found in Petersburg, in the 
mud of the Moika canal, in 1818; now preserved in the Academy of Sciences; a tooth, 
of doubtful origin, said by some to be that of a wild boar, (an animal now a stranger to 
this climate) found near Pavloosk, now in the cabinet of the Mineralogical Society; and* 
the report that an elephants tooth had once been found near the Moscow road. 
