280 TJlC Aniaicail Geologist. November, 1898 
falling water, it retreats from the river's edge more slowly than 
the contiguous bank which is alternately wet and dry. 
In short, these "promontories" result from the differential 
retreat of the banks from the water's edge, — the phenomenon 
of surface tension leading to accelerated erosii,;n where they 
are not more or less continuously kept in the wet condition. 
Of course, a number of conditions must be fulfilled to produce 
such efifects, as, — a suitable climate, — banks of just the right 
materials and texture, — minor streams, such as drain local 
swamps, for pure water;- — and these conditions exceeding in 
value the effect of the destructive work of the river in time 
of flood. 
The illustration, Plate VIII, is a view of one of these prom-' 
ontories, taken by the writer from a canoe.* It should be 
stated that the actual projection of the promontories into the 
river, as here indicated, is but temporary, — during the period 
of high water. The line of the bank beneath low water level 
is continuous. 
In spite of my having said that the local erosion suffered 
is at a minimum, owing to the purity of the water in the minor 
streams, it must be confessed that they do experience con- 
siderable loss from this source. They often have the shape of 
talus cones, and frequently, owing to differences in the hard- 
ness of strata composing them, a series of shelves is formed. 
The water, falling successively over these, hollows small ba- 
sins, and I have seen a series of such, carved from the rock, 
closely resembling those built with deposits of sinter by hot 
springs. Indeed, the fact that they are sometimes eroded 
beyond that accomplished by ordinary causes and suffered in 
common with the banks, but emphasizes the importance of 
the special acceleration of destructional work resulting from 
surface tension. 
Other effects produced by capillarity are efifloresent min- 
erals, occasional ore deposits, some dendritic minerals, etc. 
The most important ofthe efflorescent minerals are the alkali 
salts in some desert regions, and those brought to the sur- 
*They are diflficult to photograph, the river flowing very swiftly, 
and cutting deeply and sharply against the bank, so that a landing 
where they occur is usually impossible, and it is necessary to photo- 
graph them in profile, in order to show their characteristics. 
