CHARACTERISTICS AND DISTRIBUTION OF LAKKS 515 
situated in a depression of the ground not continuous with the ocean. 
The term is sometimes applied to widened parts of a river, and some- 
times to bodies of fresh or brackish water which lie along sea-coasts at 
sea-level, and may even be in direct communication with the sea. In 
English, the terms pond^ tarn^ loch, viere, and salt-pan are applied to 
smaller bodies of water according to their size and position on the 
land-surfaces. The science dealing with the study and description of 
lakes is called Limnology ^ and Limnography. 
Lakes are nearly universally distributed. They are sometimes so Distribution, 
large that an observer cannot see objects situated on the opposite 
shore, owing to the surface of the lake assuming the general curvature 
of the earth's surface; but the vast majority are of relatively small 
size. They occur at all altitudes ; some large lakes in Tibet are 15,000 
feet above the level of the sea, while the Dead Sea is 1268 feet below 
sea-level. They also vary greatly in depth and volume of water. 
In describing the Scottish fresh-water lochs they have been 
arranged according to the river basins in which they are situated, for 
it has been found that lakes are in a very special manner associated 
with the drainage areas and river systems of the globe. The primary 
source of lake-water is atmospheric precipitation, which may reach Source of 
the lakes through rain, springs, rivers, melting ice and snow, and the 
immediate run-off from the land-surfaces. This water contains sub- 
stances both in suspension and solution. The suspended matter is 
deposited for the most part on the bed of the lake, and the matter in 
solution is borne to the ocean, or accumulates in the lakes situated in 
the lowest reaches of inland drainage areas. 
In catchment basins where precipitation exceeds evaporation the Precipitation 
lakes have an outlet, and the outflowing rivers pour their waters ^^^^ evapora- 
ultimately into the ocean. The water in the lakes of these catchment 
basins is continually being renew^ed, consequently the salts in solution 
do not accumulate ; the water is drinkable, and the lakes are called 
fresh-water lakes. 
In catchment basins where evaporation exceeds precipitation — 
which is the case in all inland drainage areas — the running water of 
the system does not reach the ocean. In consequence, while the 
lakes in the higher reaches of an inland drainage area have outlet 
rivers, and their waters are fresh and drinkable, the salts in solution 
in the lakes towards the lower portions of these catchment basins 
accumulate and render the water undrinkable ; hence we find in these 
situations what are called salt lakes. ^ 
^ AiVi/T/, a lake ; A^yos, a discourse. The word " hmnography " is used sometimes 
in discussions of the variations in the level of lakes as shown by the limnograpli. 
2 It is to be understood that here and in the serpiel the word " salt " connotes 
not merely common salt, viz. sodium chloride, but any compound of an inorganic 
