26o The America?i Geologist. April, iS93 
a buff-colored tough clay. The boulders often have one side worn and 
polished, and these surfaces occasionally bear parallel strire. In its 
thickest deposits of the district here considered, ranging up to sixty 
feet, the conglomerate is perfectly unstratified; but it alternates with 
stratified beds, which sometimes inclose many boulders and pebbles, 
but occasionally none. The glacial origin of this formation was first 
suggested in 1868 by Sutherland, and has been accepted by Schenck. 
Griesbach, and Dunn; but Prof. A. H. Green (in 1889) and others 
reject this view, being more inclined to regard the conglomerate as a 
beach deposit from sea-cliff erosion, or as of igneous origin. 
Dr. Molengraaf's observations in the Vrijheid (or Vryheid) district. 
where the Dwyka conglomerate is very well developed, convince him 
of its glacial character. This district, having an extent of about 75 
miles from north to south, is crossed centrally by the parallel of 28" 
south latitude. The conglomerate is underlain by striated rock sur- 
faces, one of which, very evidently glaciated, is shown in the first plate 
of this paper. The stri.-e bear N. 28° W., as referred to the true meri- 
dian, the direction of the glacial movement having probably been thus 
northwestward, trending toward the present interior of the continent. 
The ancient drift which lies on the striated rocks is described by the 
author as follows: 
"All investigators agree that the. Dwyka conglomerate possesses 
macroscopically all the peculiarities known to belong to a glacial 
boulder clay, with this difference, that the clayey matrix has been con- 
verted into solid rock Of late I have had occasion to 
examine slides of Dwyka conglomerate from different localities, and 
I came to the conclusion that originally the matrix of the Dwyka must, 
have been a mud containing numerous small, angular fragments of 
different rocks and minerals, chiefly quartz; that, however, the origin- 
ally perfect clastic structure has been much modified by recrystalliz- 
ation, which gives the rock great resemblance to a volcanic tuff or 
breccia." 
In the final paragraph of this paper. Dr. Molengraaf refers to the 
broad extent and great thickness of this conglomerate, from which 
he infers that the Permian glacial period in the southern hemisphere 
surpassed the Pleistocene glaciation of Europe and North America. 
He writes: "I firmly believe that the glacial theory will lead to a full 
and correct insight into the mode of formation and the character of 
the lower Karoo beds, but we should never forget that the old (Per- 
mian) glaciation of the Antarctic continent must have been of greater 
importance than the well known Quaternary glaciation of the north- 
ern hemisphere. So, of course, we find all the effects of this glaciation 
on a more gigantic scale than in the northern diluvium, and indeed 
we have to accept an enormous thickness of the ice-cap and a long 
duration of this Antarctic glaciation to be able to explain the enor- 
mous thickness (the Dwyka conglomerate is in many places more than 
1,000 feet thick) and the greatly diversified development of the South 
African Permian glacial deposits." w. u. 
