DRY LAND m GEOLOGY — COLEMAN, 265 



I. C. White and Wood worth report simihir tillites between 25° and 

 30° im southern Brazil.^ New localities have been reported within 

 the last few years in Argentina - and the Falkland Islands ; ^ but only 

 few and unimportant occurrences are known in the Northern Hemi- 

 sphere outside of India. They have been reported from Herat in 

 Afghanistan, Armenia, and the Urals; and in western Europe they 

 have been described from central France* and the Frankenwald.^ 

 In North America tillites, probably of the same age, have been found 

 by Sayles near Boston ^ and by Cairnes on the Alaskan boundary.^ 



A year ago, near Penganga River, under the hot sun of India, in 

 latitude 19° or 20°, I walked across fields of ancient till strewn with 

 glaciated stones and bowlders and stood on a well-polished and stri- 

 ated surface of Vindhian limestone, as typical as can be found in 

 Ontario or northern New York. This resurrection of an ice-worked 

 surface of the Paleozoic, in what are now the sweltering Tropics, 

 gives a glacial geologist something to ponder over; and to see the 

 same things in Africa and Australia, only on a much larger scale, as 

 I have had occasion to do within the last few years, raises some of 

 the most thrilling problems in all geology. 



Our Pleistocene ice age, with its array of glacial and interglacial 

 beds, was merely an imitation on a much smaller and less impressive 

 scale of the tremendous Paleozoic ice age, which laid down in places 

 1,000 feet or more of till and included interglacial times long enough 

 to form great coal seams, as in the Greta beds of New South Wales. 



These ancient bowdder-clays and moutonnees rock surfaces of the 

 southern continents bring us face to face wdth the most dramatic 

 moment in geology, when a world, enervated by the moist, hot-house 

 conditions of the earlier Carboniferous, found itself in the grip of 

 the fiercest and longest winter of the ages, followed by the merciless 

 droughts of the Permian and Triassic. 



LATE PRE-CAMBRIAN ICE AGE. 



Still more ancient tillites have been found in a number of regions, 

 sometimes described as Lower Cambrian; at others as Uppermost 

 pre-Cambrian. In a few cases Cambrian fossils have been collected 

 in beds above the tillite, but, so far as I am aware, never beneath it. 



1 Brazilian coal fields, pp. 11-15 ; and geological expedition to Brazil and Chile. Bull. 

 Mus. Comp. Zool., Harvard, vol. 56, No. 1. 



2 Keidel : Compte Rendu, Geol. Congress, XII Session, 1914, p. 676. 



3 Halle : Geol. Mag., n. s., Dec. 5, vol. 5, pp. 264-265. 



* Compte Rendu, 1895, vol. 117, p. 255. Striated stones and angular blocks up to 

 12 or 15 cubic meters are describ»d. 



^J. D. G. G., 1893, vol. 45, p. 69. Bowlders occur scattered through unstratifled gray- 

 wacke in the upper Culm. 



« Sayles and La Forge : Science, n. s., vol. 32, pp. 723-724 ; also Harvard Bull. Mus, 

 Comp. Zool., vol. 56, No. 2. 



^ G. S. C, Mem. 67, Alaska Boundary Survey, pp. 91-92. 



