Personal and Scientific N^ews. 207 
unlike any found in the strata in which the saurian skeletons 
were embedded. All the smaller pebbles were worn smooth 
and were ellipsoidal in shape. The larger ones showed 
rounded angles, indicating, as the author says, a less amount 
of abrasion. Another point of interest lies in the fact that 
all the pebbles were conspicuous in color, either white, black, 
or pink. The inference is that the pebbles were purposely 
swallowed and served as an aid to digestion, and that the 
plesiosaurs possessed a color sense which led them to select 
the more conspicuous rock fragments. The distant shores of 
the Fort Benton and Niobrara seas must have been visited by 
the reptiles, for only along the shores were such highly in- 
durated masses to be found. Many of the fragments are of 
red quartzite and must have been derived from the quartzite 
of the Dakota group or from the horizon of the Sioux quart- 
zite. It is known that ledges of both quartzites were present 
along the shores of the interior sea in which the plesiosaurs 
of the Fort Benton and Niobrara ages lived. 
Dr. J. W. Gregory, as rerorted by N~ature (Jan. IS i. in an 
address before the Royal Geographical Society of London, on 
his recent explorations in eastern equatorial Africa, described 
the series of lakes which occupy deep rifts in the country, in- 
cluding lake Tanganyika (350 miles long. 15 to (50 miles wide. 
2,700 feet above the sea. and having a depth of more than 
1,200 feet), lake Nyassa (300 miles long and averaging 25 
miles wide, 1.500 feet above the sea. enclosed by very grand 
scenery of high mountainous plateaus ). lakes Natron. Na- 
washa, Baringo and Basso Narok (lake Rudolph). From the 
last of these a line of depression continues northward through 
Abyssinia into the Red sea : and thence it can be followed 
along a vast fault from the gulf of Akaba to the Dead sea and 
Jordan valley. "It seems not unlikely." says Dr. Gregory, 
"that tlie whole of this great line is due to one common earth 
movement of no very great age, for the traditions of the na- 
tives around Tanganyika, of the Somalis and Arabs, and of 
the destruction of Sodom and Gomorrah, ma}" have reference 
to it." On Mt. Kenia moraines of ancient glaciers were found 
5,000 feet below their present level. 
Tin: THEORY OF GLACIAL EROSION OF LAKE BASINS "I ROCK ill 
drift-bearing regions has been very ably revived by Alfred 
Russel Wallace ( The Fortnightly Bey tew, Nov. and Dec.. L893). 
It is now known, however, that deformations of the earth's 
crust b} T differential uplifts and subsidences were coincident 
with the accumulation of the ice-sheets and of the formerly 
vastly extended glaciers in mountain districts, as the Euro- 
pean Alps; so that it remains to be discriminated whether 
glacial erosion or crustal deformation contributed the princi- 
pal share in the production of these rock basins. 
