FEBRUARY 23, 1912] 
erosion. Rising rather abruptly from the coastal 
plain is the great plateau which extends to the 
basin of Victoria Nyanza. The frontal portion, 
called by Gregory the foot plateau, is underlain 
by sedimentaries of Mesozoic age. The main 
portion of the plateau is gneiss, but toward its 
-western border there have been great extravasa* 
tions of lava, which have completely covered the 
original gneiss surfaces over a belt 100 miles wide 
and extending north and south indefinitely. The 
lava flows are connected with the rifting processes 
that have formed the rift valley. The underlying 
rocks have some bearing upon the minor features 
of the different regions, but this is a matter of 
detail. The plateau as a whole from ocean to the 
Victoria Nyanza basin should be considered as a 
unit in its larger aspects. The plateau is a very 
ancient feature; it has been thoroughly pene- 
planed, though great residual masses of gneiss re- 
main, especially in the region between Voi and 
Kiu. These mound rocks in some cases rise to the 
dignity of mountain ranges. The most remarkable 
feature of the plateau is the constant, uniform 
rise of the peneplaned surface from sea level to a 
height of nearly 10,000 feet at the Man or western 
escarpment of the Rift Valley. The plateau sur- 
face is really a great beveled .'ope which rises on 
the average about 20 feet to the mile for 500 
miles. The plateau is typical of those that lie in 
the monsoon region, in that only the higher por- 
tions and those that lie near sea level are being 
acted upon by normal erosion. The intermediate 
and by far the greater area is being degraded by 
deflation and sheet-flood erosion, chiefly. There 
are two brief and widely separated rainy seasons. 
The conditions are such that, in the main, there is 
a large intake of ground water and relatively little 
run off, and hence very little dissection. In the 
interim between rainy seasons the ground becomes 
parched and dry, so that deflation becomes of 
importance and offsets dissection. The plateau 
confirms the truth of observations made in South 
Africa and elsewhere that one type of peneplana- 
tion may go on at any altitude above sea level. 
This type of peneplanation does not require desert 
conditions, as is sometimes said. Thirty inches of 
water fall annually over much of this plateau, 
but it does not require monsoon conditions where 
rainfall is concentrated in widely separated rainy 
seasons with arid or semi-arid conditions in be- 
tween. 
On the Nomenclature of Faults: Harry FIELDING 
REID. 
SCIENCE 
319 
This was a preliminary report by the chairman 
of the committee appointed by the society at the 
Baltimore meeting (1908) and was submitted for 
discussion and criticism in advance of making a 
final report at the next meeting of the society. 
Boulder Beds of the Caney Shale at Talahina, 
Oklahoma: J. B. WoopwortH. 
The Caney shales of Mississippian age in south- 
eastern Oklahoma carry grooved and striated 
stones and large boulders, all of which phenomena 
have been described by Mr. J. A. Taff, of the 
Geological Survey. The writer describes the best 
known locality near Talahina, Okla., and ascribes 
the markings on the stones and boulders to in- 
ternal rock movements accompanying the faulting 
of the beds. It is thought with Mr. Taff that the 
distribution of the boulders, aside from the nature 
of their striated surfaces, demands transportation 
by ice. Other evidence is briefly cited in support 
of the idea that the Permian Glacial period was 
preceded by signs of widely distributed ice action 
of one kind or another in the Carboniferous period 
in the northern hemisphere. 
Some Coastal Marshes South 
CHarLes A. Davis. 
A report on a continuation of the work on salt 
marshes in the vicinity of Boston, the results of 
which were reported at the Boston meeting of 
1909. The structure of salt and brackish marshes 
on the south side of Cape Cod and on Long Island 
was described and the bearing of this on the 
problem of recent coastal subsidence was discussed. 
The paper was discussed by J. B. Woodworth, 
A. W. Grabau and the author. 
Structure of the Helderberg Front: A. W. GRABAU. 
The Helderberg Front is the northern extension 
of the westernmost belt of the Appalachian folded 
area, left after extensive erosion. The former 
extent east of the Hudson is partly indicated by 
Becraft Mountain and Mt. Ida. The basal part 
is of folded Hudson strata unconformably suc- 
ceeded by late Silurie showing various phases of 
overlap. The Appalachian folds are of the usual 
asymmetric type, while the range from near Rosen- 
dale to Catskill and beyond is complicated by one 
or more pronounced overthrusts. The first of these 
was described by the author from Kingston and 
subsequently more fully discussed by Van Ingen 
and Clark. Chadwick has described a part of the 
thrust at Saugerties, and the author has deter- 
mined its character near Catskill. Several new 
sections from this last region were presented. 
The paper was discussed by J. B. Woodworth. 
of Cape Cod: 
