84 The Aui.ericd}) Geolog'iM. Janiniry, 189:^ 
MuHiit Drsirf Ishnid. 
I lUii vciT inucli indebted to professor Sli;iler Cor his kindness 
in jict'onipnnying me to Mount Desert :nid in introducing ine to 
the interesting" geology of tli;it island. Hnring oui' two days" ex- 
cursion 1 had several oi)[)ortnnities to observe that, as professor 
Shaler's map sliows, the glacial, piobably marine sediment, and 
the gra\cl and sand as well as the clay, wei'e to l)c seen only on 
the lower parts of the ishnid, j)rol)ablv up to aliont l!(Ml feet. 
Tlie first point where 1 saw auytiiing like tlie marine limit was 
two miles northeast of Somes sound, just east of the fn'riiuii on 
the western slope of McFarlands mountain. 1 j) to an apparently 
horizontal line the soil was covered with residuary boulders, but 
just above it unmodified till was exposed at the side of the road. 
The approximate hight of the shore-line was according to the an- 
eroid c* 2(14 feet ((12 m.). and according to angles measured to 
the surrounding mountains c. 210 ft. ((!() m.) + 12 feet. 
East of Somes sound, in the pass between iJrown's aiul Sar- 
gents mountains, at the hight of l»etween ;>l)(i and 200 fi^et no 
traces of marine action upon the till were seen, though the south- 
ern slope must have faced the open Atlantic, if this ever reached 
so far: but as soon as we came down to the 200 foot contour line, 
well washed and assorted material occurred abundantly as a 
gravel-b;ir east of Haddock's lower pond. T had not time to fix 
the actual limit at this locality. l)nt the approximate hight of the 
bar was according to the aneroid c. 190 feet (58 m. ). 
The curious rock benches seen at many places on the slo})es of 
the granite mountains seem to be very closely connected with tlie 
occurrence of vertical and horizontal joint lines in the rock: we 
visited several of tlu^se on Jordan's hill, Sargent's mountain and 
"the cleft. " Level Ix'uches are often formed by weathering where 
rocks are horizontally jointed, so that this important characteris- 
tic of marine action in otlu'r cases is in itself of no value here, 
luiless other common shore features, as beaches with watei' worn 
pebbles and ordinaiv cut and built tci'races of drift, together with 
marine sediment, can be shown to exist. Furthermore in several 
places the joints and the benches were inclined from 7)° to 20°, 
and nowhei'c exhibited the characteristic and very regular appear- 
ance of the r(K'k cut marine terraces in Norway and Spitzbergen. 
On the open southern surface of Sargents mountain we ob- 
*Abbrevintion of circa (about), noting an approximate measurement. 
