KENDALL : THE (;LACIER LAKES OF CLEVELAND. 
7 
rarity of beach deposits in Cleveland, and no well-defined example. 
Shore-scarps are common, but of hmited extent. The reasons 
for this deficiency appear to be (a) the rapid lowering of the 
water-level, and (6) the want of sufficient beach-forming material. 
The overflows of the Cleveland lakes were over Jurassic rocks, 
mostly soft shales ; hence they were cut down swiftly, and little 
or no beach formation resulted. 
(2) Deltas. — When a stream carrying sand or gravel enters 
standing water, the detrital materials are cast down in the form 
of a fan, the surface of which is just below the high water or 
flood-level. If debouching into the sea, the fan shelves off into 
the deep with a continuous slope, wliile a lake delta usually 
terminates \vith an abrupt face. In the Cleveland area such 
deltas are rarely seen, but some examples exist, especially in 
the valley of the Esk. They occasionally exhibit the fan-like 
form and steep scarp of lacustrine deltas, but more often they 
are simply patches of current -bedded sand and gravel occurring 
isolated at tlie beach-level where some stream has debouched, 
generally the overflow from another lake. 
(3) Floor De}X)sits. — A river flowing from a glacier is rendered 
milky-white by tlie extremely fine sediment which it carries in 
suspension. When such a river enters a lake a delta of the coarser 
detritus will first be thrown down, but the finer particles will be 
floated far out into the lake and form a finely laminated mud or 
warp. This deposit will conform itself to the undulating floor 
of the lake, whicli it will cover like a mantle. With an absence 
of vegetation on the lake bottom, such muds may be expected 
to display regular laminations, which, being parallel to the 
underlying surface, may be highly inclined. 
These characteristics are frequently displayed in the warp- 
clays of Yorkshire. A section at Danby, in Upper Eskdale 
(Fig. 2), contains a deposit indicative of lacustrine origin. Under 
red and blue clays is a leaf-clay, which contains interlaminations 
of very fine sand. A specimen sliowed 24 layers to the inch, 
each of which was found to consist of eight exceedingly fine 
laminations, making about '200 laminae to the inch. 
(4) Overflow Channels. — When an ice-sheet or glacier ob- 
structs the drainage of a country, the water is impounded so as 
