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Some Fratures oF Deutta F'orRMATION. 
By CHARLES R. DRYER. 
In August and September, 1902, the writer spent some weeks among 
the western Finger lakes in Livingston and Ontario counties, New York. 
Along the shores of Hemlock Lake his attention was attracted by many re- 
cently formed deltas which seemed to present unusual features. Each 
delta was a semi-circular pile of fine shale shingle symmetrically arranged 
around the mouth of a little gully formed by a wet weather stream. The 
level top stood about two feet above the lake surface and was bounded by 
a bank of shale which sloped downward about three feet in six to a mud 
line under water. The wash of waves had cut at the top of the slope a 
vertical cliff six inches high. The land side was bounded by a very steep 
bank of stratified shale, a por- 
tion of the general lake shore, 
which is almost everywhere pre- 
cipitous. From the mouth of 
the gully a groove a foot wide 
and six inches deep extended 
straight out half way or more 
across the top of the delta, but 
in no case reached the water’s 
edge. Along the sides of the 
groove lay sticks of wood and 
fragments of shale of relatively 
large size. One medium sized 
delta measured thirty-one feet 
, ca se F Fig. 1. Model of Torrential Delta in 
by twenty-six in diameter. No Shale Gravel. 
camera was at hand, but sketches were made from which a rough model 
was constructed and photographed. (Fig. 1.) 
The interpretation of the phenomena seemed plain. These deltas were 
built during an exceptionally violent storm which filled the gully with a 
rushing torrent and raised the level of the lake. The force of the stream 
was abruptly checked at lake level and its load was deposited in the form 
of a fan-like delta. Toward the last of the storm the stream striking the 
