140 The American Geologist. March, 208s 
Uber H. v. Meyer’s Mastodon Humboldti Cuv.? aus Mex 
ico. (Neues Jahrb. f. Min.) 
1888. 
Macraster, eine neue Spatangoiden-Gattung aus der 
Kreide von Texas. Mit 1 Tafel. (Neues Jahrb. f. Min.) 
Uber eine durch die Haufigkeit Hippuriten-artiger Cham- 
iden ausgezeichnete Fauna der oberturonen Kreide von Texas. 
(Palaeontol. Abh. Bd. IV. 3 Tafeln. 
School of Geology, University of Texas. 
THE RATE OF LATERAL EROSION AT NIAGARA. 
By PROF. G. FREDERICK WRIGHT, Oberlin, Ohio. 
PLATES VI-VIII. 
In the Popular Science Monthly for June, t899, I presented 
the result of certain observations the year before upon the later- 
al erosion of the walls of the gorge of Niagara river near the 
edge of the escarpment at Lewiston, seven miles below the falls. 
The reader is referred to that article for several photographs 
and a profile section, drawn to scale, showing the extent of 
the enlargement at the mouth of the gorge upon the east side. 
Briefly the results of the measurements then made are, that 
the Niagara limestone, which is the upper stratum throughout 
and is here 340 feet above the river, has been undermined and 
broken off 388 feet since the erosion of the gorge began. But, 
in order to get an approximate idea of the time required to ac- 
complish that amount of lateral enlargement, it is necessary 
to obtain the rate at which the face of the precipice is crumb- 
ling away under the influence of subaérial agencies. To get 
light upon this point, I was again commissioned in 1899, by 
the New York Central Railroad to spend such time as was 
necessary for investigations leading to more definite results. 
In pursuance of this, a week was spent, with competent en- 
gineers as assistants, in determining the actual extent to which 
the crumbling away of the rocks has proceeded since the rail- 
road was built, in 1854. 
The accompanying diagram shows how the road crosses 
the several strata as it gradually descends the face of the 
gorge. (Plate VI.) It is necessary only to add: 
