PERMOCARBONIFEROUS ICE AGE 185 



which cast doubt on the new reports from the far east and south. Was 

 not the Carboniferous a tropical time, even in the Arctic regions ! Gla- 

 ciers and the steamy coal swamps did not mix well together. 



Since then, however, many northern geologists, including expert gla- 

 cialists, have studied these marvelous deposits, and for a number of years 

 no one has doubted their glacial origin, in spite of the fact that most of 

 the localities are in what are now warm temperate or even tropical re- 

 gions. All tbe evidences for the ice-action on a large scale found in our 

 Pleistocene are repeated, with the difference that the Pleistocene till 

 ceases about 38° from the equator, while the Talchir tillite in India 

 reaches well within tbe tropics (18° north) and Permocarboniferous 

 tillite in West Australia touches the tropics. In South Africa the Dwyka 

 tillite reaches 24° 30', or even 22 , 7 and I. C. White and Woodworth 

 report similar tillites between 25° and 30° in southern Brazil. 8 New 

 localities have been reported within the last few years in Argentina 9 and 

 the Falkland islands; 10 but only few and unimportant occurrences are 

 known in the northern hemisphere 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 Prance 11 and the 

 Frankenwald. 12 In North America tillites, probably of the same age, 

 have been found by Sayles near Boston 13 and by Cairnes on the Alaskan 

 boundary. 14 



A year ago, near Penganga Eiver, under the hot sun of India, in lati- 

 tude 19° or 20°, I walked across fields of ancient till strewn with gla- 

 ciated stones and boulders, and stood on a well polished and striated sur- 

 face 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 Aus- 

 tralia, 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. 



7 For literature see Glacial periods and their bearing on geological theories, by the 

 writer. Bull. Geol. Soc. Am., vol. 19, pp. 347-366 ; and Schuchert : Climates of geologic 

 time. Carnegie Inst., Pub. No. 192, pp. 263-298. 



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

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



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



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



11 Compte Rendu, 1895, vol. cxvii, p. 255. Striated stones and angular blocks up to 

 12 or 15 cubic meters are described. 



12 J. D. G. G., 1893, vol. xlv, p. 69. Boulders occur scattered through unstratified 

 graywacke in the upper Culm. 



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

 Comp. Zool., vol. lvi, No. 2. 



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



