50 
MUSEUM BULLETIN NO. 2. 
Cliff recession is indeed accelerated by coastal subsidence; but 
it takes place on any fully matured shore-line, as a part of the 
normal sequence of changes, and even on young shore-lines 
where the initial slope is steep. 
That rapid cliff recession does not necessarily indicate that 
subsidence is in progress is seen in the case of the west shore of 
Lake Michigan, between Milwaukee and Chicago. According 
to Dr. Edmund Andrews, 1 the average rate of recession of this 
cliffed coast, prior to 1870, was over five feet a year. In other 
words, although the cliffs along the west shore of Lake Michigan 
are higher than those on the northeast coast of New Brunswick, 
their average rate of retreat is faster. Locally, cliff recession 
as fast as thirty or forty feet has been observed on the Wisconsin 
shore. 2 This destruction of cliffs by the waves of Lake Michigan 
cannot be attributed to a rise in level of the water on the shore; 
for the surveys cover a long period of years, during which the 
changes of level of the lakes have been slight, and as often 
downward as upward. 3 
Drowned Valleys . — In a letter in Science, 4 discussing the 
question of modern stability of the Atlantic coast, Mr. T. L. 
Casey points to the well-known estuarine coast of Maryland as 
1 ‘positive evidence of progressive subsidence ... in 
recent times.” If the drowned valleys of Chesapeake bay can 
thus be appealed to as evidence that the coast of Maryland is 
now sinking, the same argument could be applied to the equally 
typical dendritic estuaries of Gloucester, Cumberland, and Kent 
counties, in New Brunswick. It seems necessary, therefore, 
to anticipate the use — or, more accurately, the misuse — of such 
evidence, by pointing out the fallacy in it. Drowned valleys 
simply indicate that the land once stood higher than now; they 
do not indicate the date of the drowning, and do not prove that 
1 Edmund Andrews: The North American Lakes considered as Chronometers 
of Post-glacial time. Transactions of the Chicago Academy of Sciences, vol. 2, 
1870, pp. 1-23. 
2 J. W. Goldthwait: Abandoned shore-tines of eastern Wisconsin. Wisconsin 
Geological and Natural History Survey, Bull. No. 17. 1907, pp. 58-59. 
3 For similar testimony from the shore of Lake Huron, and information as to 
the fluctuations in level of the Great Lakes, see A. C. Lane: Geological report on 
Huron County, Michigan. Geol. Survey of Michigan, vol. 7, 1900, pp. 78-85, and 
Plate 5. 
4 T. L. Casey: Subsidence of the Atlantic shore-line. Science, vol. 34, 1911, pp. 
80-81. 
