E. T. Mellor — Glacial Conglomerate of South Africa. 113 



of the Transvaal. They are, however, frequently reduced to 

 patches consisting almost entirely of the Glacial Conglomerate 

 and associated beds. The copious sandy drift shed by these 

 outliers frequently renders their examination difficult, but in 

 some cases they offer more than usually good opportunities for 

 the study of the Glacial Conglomerate and its relationships to 

 the underlying rocks. In the district here more especially 

 referred to, the glacial deposits consist for the most part of a 

 conglomerate showing all the characters to be expected in one 

 formed beneath an extensive ice-sheet. This conglomerate is 



very irregular in distribution, and varies greatly in thickness 

 within short distances, partly in consequence of its original 

 deposition on an irregular land surface, and partly as a result 

 of subsequent denudation. Its average thickness is about fifty 

 feet. In depth the rock is sometimes greenish in color, but 

 at the surface it is usually light yellow, and crops out in char- 

 acteristic humpy masses (see fig. 1). The matrix is a sandy- 

 looking material consisting of sharply angular fragments of 

 quartz and of various rocks — quartzites, hard shales, felsites, 

 granophyres —common in the district. These angular frag- 

 ments vary in size from the smallest particles to pieces several 

 inches in diameter. Irregularly distributed through the 

 matrix, and with a conspicuous absence of any sort of arrange- 

 ment as to size or orientation, occur abundant pebbles and 



Am. Jour. Sci. — Fourth Series, Yol. XX, No. 116. — August, 1905. 



