234 The American Geologist. April, isgo 
Mass motion to this extent and of this nature is, I think, 
seldom realized as an actual occurrence. But if it is real as 
above shown — if strata have slidden bodily over strata for 
miles, and whole counties have been shoved for long distances 
out of their previous places over "thrust-planes" lying almost 
horizontal, it is obvious that great lateral displacement must 
be recognized as an important geological factor in disturbed 
regions. A striking illustration may be found in the very 
area now under consideration. During the Appalachian Rev- 
olution or that earlier one in mid-palseozoic days the folds 
composing the South mountain chain actually snapped across 
under the strain, and one part — the northeastern — was shoved 
forward three miles beyond the other — the southwestern. This 
cross-fracture and thrust may now be recognized in a notch 
of that extent in the mountain-wall of Franklin county near 
Chambersburg. 
How long these stupendous changes occupied it is of course 
impossible to tell, but there are reasons for believing that they 
were not sudden or catastrophic. They probably progressed 
slowly so that the surface was not much disturbed and they 
may have occupied the whole of the long interval between 
palseozoic and mesozoic time, or even a longer period. This, 
however, does not now concern us. We have shown that the 
great sea of Pennsylvania was converted into a swamp and 
flat, and that on this swampy flat huge arches of bent strata 
were reared to a hight that it is difficult now to realize. It 
remains to show how from this complex of arches the modern 
Pennsylvania has been slowly constructed as mesozoic and 
tertiary time passed by. In other words we may here close 
the first volume in the history. 
EDITORIAL COMMENT. 
AV\/^ARD OF THE HaYDEN MEMORIAL MEDAL TO PrOF. JaMES 
Hall, LL.D. The widow of Dr. Ferdinand V. Hayden, late 
Director of the U. S. geological survey, executed two years ago 
the following deed of trust, to which is appended the official 
acceptance of the same by the designated trustee : 
Know all men by these presents that I, Emma W. Hayden, of the 
city of Philadelphia, in commemoration of my dearly beloved husband 
