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The question of the altitude of the highest marine 
beach in this district is complicated by the presence both 
in the Champlain valley and in the Ontario valley of higher 
shore lines which have generally been referred to temporary 
pro-glacial lakes, that is to say, lakes in basins whose 
natural northern outlets were for a time covered by the 
ice sheet as it withdrew from the lowlands but still over- 
lapped the Covey Hill highlands and those of northern 
Vermont. According to Professor J. B. Woodworth 
[10, pp. 66-265] the higher beaches of the Champlain 
valley which would reach Covey hill at an altitude 
above 700 feet (213-4 m.), if they extended as far 
north as that, do not continue around the north side of 
the hill, but seem to vanish some where between West 
Chazy, New York and the international boundary. It 
is inferred from this that the ice sheet covered Covey hill 
while these beaches formed ina ‘‘glacial Lake Champlain.” 
On the contrary, according to Professor H. L. Fairchild 
there are beaches and deltas of a water plane above 700 
feet (213-4 m.) on the Ontario side, which may perhaps be 
carried around the Covey Hill district by correlation 
with obscure delta deposits and found to correspond with 
the distinct beaches at West Chazy. The water plane 
thus restored is believed by Fairchild to be marine, and 
to extend over the Champlain-Hudson divide at Fort 
Edward, N.Y. and down the Hudson river to sea level 
at New York city. The observations upon which Professor 
Fairchild bases this conclusion have not yet been published. 
The importance of so critical a correlation of beaches on 
the Ontario and Champlain sides of the Adirondacks 
demands for satisfactory support a very large number 
of accurate measurements of altitude along the shore line 
in question. 
The determination of the upper marine limit at Covey 
hill can hardly be reached by a search for marine shells 
however diligent. Rarely have shells been discovered 
at or near the line of maximum submergence. Montreal 
and Riviere du Loup are the only localities where this has 
been the case. Shells can be relied upon simply as an 
index to the fact that the sea stood at least as high as they 
occur; the marine beaches ordinarily extend up to much 
higher altitudes. This is due not simply to the failure to 
look carefully for shells at the upper limit but apparently to 
the fact that shellfish were most numerous and best pre- 
