242 R. D. Trving—Divisibility of the Archean. 
lamination directions of the older schists and newer slates, 
chart, the lamination directions vary also. Such a relation of 
lamination planes as this—discordance at some points, accord- 
ance at others—is precisely what should be expected along an 
unconformable contact line, and could occur under no other 
circumstances; the underlying rocks being, in part at least, 
certainly of sedimentary origin. It is no argument against 
this view, to maintain that the lamination of the older set of 
rocks is in this case what is known to geologists as foliation, 
and not the result of sedimentation. I have little doubt that 
it is often foliation, i. e. a structure in some way due to the 
intense squeezing which these older schists have undergone, 
and one which very possibly often occupies a position quite 
oblique to the original bedding directions. Manifestly, how- 
ever, this foliation must have been produced before the depost- 
tion of the first of the overlying slaty rocks, for otherwise the 
latter must have been affected also by a foliation similar in 
character and direction. But there is no true foliation about 
them, and what there is occasionally approaching it is always 
manifestly parallel to the bedding planes, and thus commonly 
discordant with that of the schists below. The occurrence of 
newer rocks is to be made out, not merely from closely approx 
imated exposures of the two formations but from actual visible 
ntacts. Descriptions of both of these localities have already 
been published.* The contacts are certainly not those of 
eruptives with previously formed sediments; on the contrary, 
they are exactly what they should be, had the lower schists 
formed an irregular bottom upon which the newer slates were 
deposited. 
Still another thing going to show the complete distinctnes 
between the two sets of rocks we are considering is the plenti- 
ful occurrence, in certain layers of the higher series, of frag- 
ments derived from the lower one. These fragments occur at 
times a third of the way up in the newer series. They are 
* Geol. of Wis., vol. iii, pp. 98, 116, 117. Also Annual Report of Geol. Survey 
of Wisconsin for 1877, p. 26. 
