120 Dr Fleming's Uemarks on the Modern Strata. 
4. aS' 27^.— Wherever there are hollows filled with still-water^ 
whether these support the character of inland-lakes, or of the 
sea, processes are going forward, which have a tendency to fill 
them up ; and the matter deposited we here venture to term 
Sitt. 
^ The Lacustrine Silt is, in some instances, saline, arising from 
the evaporation which the waters experience during the summer 
season. Of these, however, we have no examples in this coun- 
try. The more common lacustrine silt, consists of the fine parti- 
cles of detritus, carried into the lake by rivers or temporary 
streams, and slowly deported from its state of suspension. It 
is increased by the supply produced on the margin of the lake 
by the disintegration, decomposition, and attrition of the rocks 
which prevail. As the lake becomes shallower, plants and ani- 
mals multiply, and contribute by their relics, to accelerate the 
process. In ordinary cases, this silt consists of an inferior bed 
of sand, with an incumbent bed uf peat. In some cases there 
is an intervening bed of marl. The marl consists of the relics 
of those testaceous mollusca, which feed upon the plants of the 
lake, and the animalcula of its waters, including phytivorous and 
carnivorous, pulmoniferous and branchiferous species. The 
marl-bed likewise receives as the effect of subsidence, the skele- 
tons of the animals which have been drowned, while feeding on 
the marshy borders of the lake, or have been conveyed into it by 
floods. The character of the lowest or earthy bed, depends on 
the character of the bed of the lake, and the materials of the sur- 
rounding hills. Sometimes it is a sandy-clay, or a clayey-sand ; 
while, in other instances, it is a pure clay, consisting chiefly of 
aluminous earth, or a pure siliceous mud, usually termed Kaolin. 
When a lake of this kind, situate on a level with the sea, and 
near the coast, has been filled up, chiefly with earthy matter, 
the surface of which has passed into soil, fit for the support of 
trees, the seaward barrier may be broken down, drainage by 
the tide may take place, followed by subsidence ; and that soil 
may be daily covered at flood, which formerly was out of its 
reach, and above its level. In a paper published some time ago 
in the Transactions of the Royal Society of Edinburgh, vol. ix. 
p. 419, I endeavoured to explain the formation of submarine 
Jbrests, agreeably to the preceding views. Subsequently, ano- 
