140 The American Geologist. February, 1894 
The author used the case of the Catskill sandstone as an illustration. 
The Catskill '•formation," "group," or "period," is a rock formation 
developed along the northern part of the Appalachian system; but it is 
not, and it does not represent, any particular geological period of time. 
In western New York the whole of the Devonian era is represented in 
stratified deposits without unconformity, and no Catskill formation 
appears among them. Along the Cayuga lake section the Catskill for- 
mation appears at the top of the Devonian system, and is late Neode- 
vonian in age. Along through Otsego and Delaware counties there was 
a temporary appearance of the Catskill formation in the midst of rocks 
of early Neodevonian age, called the Oneonta group, but the Catskill 
proper of that section was formed in the latter half of the Neodevonian. 
In eastern New York the deposits of the whole Neodevonian are the 
Catskill formation. In Maine the rocks from the top of the Oriskany 
sandstone to the Carboniferous all may be defined as the Catskill 
formation, which is in that region Eodevonian, Mesodevonian and Neo- 
devonian in age. A time definition, therefore, is not appropriate to the 
Catskill formation, and nothing is to be gained by attempting to use it 
in that sense. 
Prof. Alpheus Hyatt remarked, in discussion of this paper, that the 
threefold division of great periods is a matter of much interest. It 
depends, apparently, on an underlying principle. 
Sir William Dawson commented on this, that, if there was anything 
in a period at all, it must have a beginning, a middle, and an end! 
9. Johann David Sahoepff, and his contributions to North Amercan 
geology. Geokge H. Williams, Baltimore, Md. This almost forgotten 
contributor to the geology of our country came to America during the 
Revolutionary war as a surgeon of the German troops employed by 
England. His observations upon the geology between the Atlantic coast 
and the Appalachian mountains from Rhode Island to Florida, and 
especially in Pennsylvania, Maryland, and Virginia, were published in 
a book, "Beitrage zur Mineralogischen Kenntniss des ostlichen Theils 
von Nord America," dated 1787, in which he, with remarkable accuracy, 
foreshadowed most of the recent general conclusions concerning the 
region. The only copy of the volume heretofore known to be in this 
country is in the state library at Albany, N. Y., but Prof. Williams found 
on application that copies of the original edition are still on sale in 
Germany and can be had at a low price. 
10. Relations of synclines of deposition to ancient shore lines 
Bailey Willis. Washington, D. C. (Read by title.) The data in obser- 
vations and experiments forming the basis of this paper will be dis- 
cussed more fully in a memoir, "Mechanics of Appalachian Structure," 
in the Thirteenth Annual Report of the U. S. Geological Survey. 
A syncline of deposition is a trough resulting in strata through sub- 
sidence under a locally thick accumulation of later sediments. The 
definition is independent of the hypothesis that the strata sink because 
they are loaded, as it is of the alternative theory that the sinking of the 
strata afforded opportunity for unusually copious deposition. Subsid- 
ence has often proceeded as sediments accumulated. 
The bulk of sediments is deposited near shore. When erosion is pro- 
ceeding rapidly in a deep residual mantle, providing great quantities of 
sediment, the deposit along shore is excessive, and the resulting forma- 
tion thins gradually seaward. This may be seen in many thick deposits 
of shale. 
Subsiding under such a deposit, older strata will assume a decided 
dip from the shore to the line of maximum deposition: and they will 
rise from that line seaward with a gentler inclination.* For instance 
♦Am, Jour. Science, Sept., 1893. "Conditions of Appalachian Faulting," by Bailey 
"Willi* and C. Willard Hayes. 
