1882 .] 
845 
[Davis. 
from such weathering might sometimes produce hollows that were 
ater, in a more humid condition of climate, filled with water. 
The question for us is not so much whether this explanation is 
true, for given the necessary time and conditions it is very possi- 
ble, but whether the process ever actually occurred. Certain small 
pools held in rock-basins in Mongolia 1 were first ascribed to it> 
but little time was given to their study, and the explanation was 
proposed rather as a suggestion than as a final solution of the 
difficulty they presented. 
B. 8. Solution Basins. The removal of limestone, gypsum or 
salt in solution in water being independent of' a stream’s velocity 
and of gravity, may in some cases form a hollow lower than its 
outlet ; but while this has probably aided in making many valleys 
and lakes, it is difficult to name any basins of which it has been 
the sole cause. 
The carboniferous limestone of the Central Plain of Ireland 
contains numerous lakes, many of which follow the irregularities 
of the limestone among other rocks so closely as to imply that they 
are dependent upon its solubility ; Loughs Erne (Upper and 
Lower), Ree and Derg, besides many smaller ones, are of this 
kind. 2 How completely they are, dependent upon solution, it is 
difficult to say, as the country in which they stand has been glaci- 
ated and contains much drift which may well complicate their 
origin. 
The efficacy of the solvent power of water to produce lakes was 
recognized by Playfair, the pools in the marls of Cheshire serv- 
ing as examples : he saw also the difficulty of forming lakes by 
other kinds of erosion, and in the case of Lake Geneva suggested 
that its basin might have been dissolved out of a great deposit of 
salt, of which some remains are still to be found at Bex, a little 
above the lake. 3 A similar cause has been surmised as an aid in 
forming our Great Lakes. Sink-hole lakes, related to this species, - 
are described later. 
1 Purapelly, Geol. Researches in China, Mongolia and Japan, 72, 73. Minute exam- 
ples, five feet in diameter, are described by Ormerod, On the Rock-Basins in the Gran- 
ite of the Dartmoor District, Devonshire. Geol. Soc. Journ., xv, 1859, 16-23. 
2 Hull, Phys. Geol. and Geog. of Ireland, 198. 
8 Illustrations of the Huttonian Theory, 1802, 364. 
