1872.] 533 [Perry. 
and also part of the next or Jurassic period.” 1 Among other points 
here suggested, the question may be fairly asked, whether this estu- 
ary had not an earlier origin than supposed; whether it does not date 
back, if not to the beginning, at least to a portion of the Permian 
period; and thus, whether the lower sandstone — that, for instance, 
on the western border in the neighborhood of Greenfield —be not 
of Permian (or Dyassic) age, and not Triassic. It may be also 
asked, whether the next higher portion be Permian and Triassic, or 
Triassic and Lyassic, or simply Triassic; and finally, whether the 
uppermost beds be merely Triassic, or Triassic and Jurassic. These 
points, respecting which Professor Dana seems to have no doubt, for 
he calls all the beds Triassic and Jurassic, are beset with difficulties 
of no ordinary magnitude. They are accordingly brought forward 
with diffidence, and still with hope that new light will be speedily 
thrown upon them, such light as will place the matter beyond the 
possibility of mistake. Regarding them as by no means settled on a 
satisfactory basis, I have raised these questions as preliminary to a 
more searching investigation and adequate determination, which I 
hope soon to make, of the relative age or ages of the great sandstone 
deposits of the Connecticut valley. 
Ill THE POST-TERTIARY TIMES 
Are now to receive, after these introductory considerations, more 
special notice. It is perhaps best to present them first of all in 
outline. As Professor Dana suggests, they may be conveniently 
divided, according to the indication of the rocks met with in New 
England, into subordinate periods. Beginning with the older, he 
designates his divisions as, (1) the Glacial epoch, (2) the Champlain, 
and (3) the Terrace or Recent. The term “epoch” as thus used to 
indicate a lapse of time, is, no doubt, open to objection. It is prop- 
erly applicable, not so much to a period or an extension, as to a 
point of time — to the moment that marks a culmination or a crisis. 
Thus“ epoch” refers to a point, “period” to a duration — that is, 
the way from one epoch or point, round to another point — of time.. 
If it be joined to a word usually expressive of duration, it should 
simply mark it as a point, or halting-place, according to the original 
meaning of the word among kindred durations; as an acme, and 
1 Paper cited, p. 46. 
