1894. | NEW YORK ACADEMY OF SCIENCES. 17 
phenomenon was written by J. W. Spencer,* and it is a most 
graphic illustration of the points in question. 
In this connection I also wish to call attention to the recently 
published experiments by Bailey Willis} in the crumpling of 
plastic strata by a force advancing from one direction. If we 
compare his original models to sections of the former coastal 
plain and the force exerted by his piston to the force exerted by 
the advancing ice front, we have a parallel series of examples, 
and some of the pictures of the models after compression would 
serve as excellent charts of sections through the morainal region 
of the coastal plain to-day, particularly plates xev. and xevi. of 
the work mentioned. Iam also pleased to say that after having 
come to the above conclusion I wrote to Mr. Willis and received 
from him a reply, from which I quote as follows: ‘ Deformation 
in stratified layers under pressure occurs in different manner 
under three distinct conditions. * * * Now in your case the 
plastic quality of the clay affords a condition similar to that of 
excessive load upon more solid material. This was true also of 
models xcv. and xevi, to which you refer. I presume there is no 
question but what the ice sheet was competent to produce the 
deformation.” 
Under the circumstances I am inclined to accept these con- 
clusions as final until proven otherwise by evidence to the con- 
trary,and to consider the phenomena of folding and dislocations 
as the visible effects of glaciation, from which we may calculate 
the extent of the cause. In other words, to utilize them as 
data from which to calculate the magnitude and extent of 
glacial action in quaternary time in this vicinity—a task, how- 
ever, which I cheerfully leave to the glacialists. 
COMPARISON OF THE THEORIES OF MOUNTAIN-MAKING FORCES AND 
ICE ACTION. 
Considering the facts adduced, we have, in favor of the 
theory of ice action, the general structure of the morainal 
region of the coastal plain; the uniform coincidence of distorted 
coastal plain strata with the line of the moraine; the absence of 
any distortions where the moraine does not reach the plain ; 
the much more pronounced distortions at localities where the 
moraine indicates an extensive advance of the ice over the plain 
*« 4 Jandslide at Brantford, Ontario, illustrating the Effects of Thrusts upon yield- 
ing Strata,’’ Am. Nat. xxi. (1887) 267-269, illustrated. 
+‘*The Mechanics of Appalachian Structure,’ Thirteenth Ann. Rept. U.S. G.S. 
(1891-92) 217-281, pl. Ixxy.-xcvi. 
TRANSACTIONS N. Y. ACAD. Scr., Vol. XIV., Sig. 2, Dec. 4, 1894. 
