Davis.] 
874 
[January 18 , 
the others, as Utah Lake by the Jordan into Great Salt. They 
are common in many half-desert regions ; the smaller ones fre- 
quently disappear in the dry season, leaving salt or alkaline 2 
incrustations on their bed ; like all examples of the species they 
are shallow, with flat borders, and are generally less attractive 
than any others we have to note. Prejewalski describes one of 
these brackish pools in the barren, cheerless plains of Eastern 
Mongolia as giving anything but savory water to the caravans 
that stop by its margin ; and another in the same country, some 
thirty miles in circumference, but now all evaporated and leaving 
in its place a bed of salt two to six feet thick, which the swans flying 
past mistake for a sheet of water. 1 In southern Africa there is a 
stream noted for changing its direction of flow with the high and 
low water-level of a salt lake, being therefore alternately an afflu- 
ent and an effluent. 2 In South Australia the overflow of one of 
these lakes at high water makes its outlet run salt, but it freshens 
later in the season 3 ; the very variable area of the Australian 
Lakes with the time of year caused much difficulty in the identifi- 
cation of sheets of water reported by different expeditions fifty 
years ago. Lake Sistan, into which the Helmund river of Afghan- 
istan flows, varies so greatly in size and salinity that different 
explorers have reported it fresh and salt, according as they 
saw it near its inlet in the wet season or later in the year when 
it was nearly dried up. 
The Chottes, 4 or salt depressions of Algeria, of which the 
proposed flooding has excited much comment, and the Bitter 
Lakes 5 of the Isthmus of Suez, restored to something like their 
original size by the opening of -the Canal, are probably the com- 
bined results of elevation and evaporation. 
Hybrids frequently occur between this species and the Delta 
Lakes. 
C. 13. dlacial Drift Basins. Lakes of this origin have 
already been alluded to (C. 3, 4), and may now be described 
1 Mongolia, 1876 (traus. by E. D. Morgan), I, 116; ii. 2. 
2 Holub, Roy. Geogr. Soc. Proc. 1880. 
3 Roy. Geogr. Soc. Journ.,n, 1832, 121 ; vi, 1836, 434. 
4 Martins et Desor, Comptes Rendus, lxxxviii, 1879, 268. 
5 F. de Lesseps, Sur les Lacs amers de I’isthme de Suez, Comptes Rendus, lxxviii, 
1874, 1740. 
