533 
Quartz Rock of the Lackey Hill, &c. 
rivers, and the bursting of alpine lakes, and similar minor causes 
which operate daily, and partially within the sphere of our own 
observation. 
The Hon. Wm. Strang ways, in a valuable Synoptic Table of the 
Formations near Petersburg, published by him during his late 
residence in that city, has adopted with great advantage this division 
between diluvian and post-diluvian formations ; distinguishing them 
by the name of diluvium and alluvium. He dates the commence- 
ment of the alluvium from the period of the retreat of the last waters 
that have covered the earth, and includes under it — 1, Drift sand 
marine, or inland ; 2, Marsh land, composed of mud deposited by 
rivers ; 3, Peat ; 4, Calcareous tuf. All these formations are re- 
ferable to causes that are still in daily action ; under the term 
diluvium he includes the superficial gravel beds that lie indis- 
criminately on all strata of anti-diluvian origin, and are composed 
of a mixt detritus of pebbles, sand, and clay, torn down from 
formations of all ages, except alluvial, and also the blocks of granite 
and other fragments of primitive and secondary rocks, that are 
scattered over the plains and low hills of that part of the north of 
Europe, either mixt with the superficial gravel, or lying insulated 
in situations to which they must have been drifted from very 
considerable distances, as there is no matrix near them from which 
they could by possibility have been derived. He has omitted to 
mention beds of gravel produced locally by torrents and rapid rivers, 
because the flat condition of the district on which his synoptic table 
is founded, has allowed no gravel of this kind to be transported to 
so great a distance from the hills or mountains, from the daily 
detritus of which it is immediately derived. 
A well digested and valuable comparative account of the mode 
of action and effect of rivers and mountain torrents, shewing that the 
