272 
Missouri. Meanders with sloping tongues, form a class by themselves, 
and have been most fully discussed by C. F. Marbut of the Missouri Geo- 
logical Survey.* He publishes maps of the meanders of the Grand and 
Flat Rivers, but none of them are quite equal to the Vernon tangle of the 
Muscatatuck. 
Two hypotheses have been suggested to account for meanders which 
are not due to flood-plain conditions. Prof. W. M. Davis has suggested7 
that they may be superimposed or inherited from a former flood-plain con- 
dition. In some previous period the stream has reached base level and 
developed flood-plain meanders. The basin has been subsequently ele- 
vated and the stream in its new cycle has cut its old meanders straight 
down into the plateau. This may serve to explain meanders in which the 
tongues are headlands, but evidently will not apply to those of the Mus- 
catatuck, which are not cut straight down. 
Winslowz thinks such meanders are due to a normal growth and de- 
velopment from an originally crooked consequent course. The germ of 
the present remarkable loops existed in the slightly irregular surface of 
the country over which the stream first began to flow. As it corraded its 
channel more deeply it cut away the convex sides of its bends. It thus 
became more and more crooked, and by a combination of vertical and 
lateral corrasion, it slid or sidled down the long slopes of the tongues. 
The meanders of the Muscatatuck seem to be better accounted for 
by development than by inheritance; but the process has been somewhat 
modified by peculiar conditions. During the cutting of the first seventy 
or eighty feet, lateral corrasion was more rapid than vertical, and the 
long gentle slopes of the tongues were formed. At about the 675-foot 
level vertical corrasion, for some reason, became more rapid and a twenty- 
foot terrace was formed. At the 655-foot level the stream came down 
upon the hard and massive Niagara beds, or the corniferous limestone 
which thinly overlies them. Vertical corrasion seems to have ceased for 
a long period, during which the stream slid laterally and planed off the 
broad, flat points of Tongues No. 1 and No. 3. Then came a decided change, 
probably an elevation of the land and an increase ofthe slope, which has 
enabled the stream to cut its channel almost vertically downward into 
* Mi-souri Geological Survey, Vol. X, p. 98. 
+ Science, Vol. 22, p. 276. 
{ Science, Vol. 25, p. 31. 
