BANDED SLATES WITH OTHER TILLITES. 53 
The illustrations which Halle shows are strikingly similar to the Squantum 
slate, and one of these cuts is reproduced here (Fig. 2). It was very natural 
that Halle should have thought of the similarity 
between the banded slates and the laminated 
glacial clays. He was without doubt very 
familiar with the work of de Geer and also had 
a personal knowledge of the glacial clays. 
In 1912 Sederholm of Sweden advanced 
the seasonal theory to account for banding in 
the Bothnian schists. There is one important 
difference between the work of Halle and Seder- 
holm. The former had some undoubted glacial 
beds closely related to his banded slate, while 
the latter just assumed that the banding in the 
Bothnian schists was of an annual nature and Fig. 2. Laminated claystone. Dar- 
: ‘ : in Harbour. F Halle: Bull. 1. 
resembled the banding in glacial clays. In the Here aie. Upeaie, ait — cna 
former case the evidence is much easier to 
accept than in the latter. In writing of the banding in the Bothnian Schists 
Sederholm records: 
“Among the Bothnian schists of Tammerfors occur some whose regular alternation of 
sandy and clayish beds recalls very much that of the glacial clays of the same region, and is 
very probably, like that, due to an alternation of seasons.” SEDERHOLM, 1912, p. 687. 
This observation of Sederholm’s although very important lacks the firm 
foundation on which the observations of Halle rest, namely, tillite beds. 
After discovering that banded slates are associated with two tillites in 
widely separated parts of the earth, it is natural to inquire af once whether 
other tillites may not have such related slates. After a conference with A. P. 
Coleman of Toronto, I find that the lower. Huronian tillite at Cobalt is very 
similar to the banded slates at Squantum. Barrell (1915, p. 112, 113) men- 
tions these Cobalt slates at the foot of Cobalt Lake. 
Recently I noticed in the Geological Museum at Harvard, a specimen 
which had been on exhibition for about ten years but which had not been particu- 
larly significant heretofore. In 1906, Mr. A. W. Rogers, Director of the Geo- 
logical Survey of South Africa, very kindly sent a set of specimens of tillite from 
the Griqua Town series of South Africa. The specimen in question is a well- 
banded black and brown jasper. The banding is so regular that in view of the 
