=The horologe of late glacial time in Scandinavia.=—A glacial timepiece of somewhat different construction and of greater refinement has been made use of in Scandinavia to derive the “geochronology of the last 12,000 years.” Instead of retreating over the land and impounding the drainage as it did so, the latest continental glacier of Scandinavia ended below sea level, and as it retired, its great subglacial river laid down a giant esker known as the Stockholm Os, which was bordered by a delta and fringed on either side by water-laid moraines of the block type. These recessional moraines are upon the average less than 1000 feet apart, and are believed to have each been formed in a single season. The delta deposits which surround the esker are of thin-banded clay, and as an additional uppermost band is found outside every moraine, these bands are also believed to represent each the delta deposit of a single year. In studies extending over many years, Baron de Geer, with the aid of a large body of student helpers, has succeeded in completing a count of moraines and clay layers, and so in determining the time to be 12,000 years since the ice front of the latest continental glacier lay across southern Sweden. The fertility of conception and the thoroughness of execution of this epoch-making investigation recommend its conclusion to the scientific reader. READING REFERENCES FOR CHAPTER XXV G. K. GILBERT. Niagara Falls and their History, Nat. Geogr. Soc. Mon., vol. 1, No. 7, 1895, pp. 203-236. F. B. TAYLOR. Origin of the Gorge of the Whirlpool Rapids at Niagara, Bull. Geol. Soc. Am., vol. 9, 1898, pp. 59-84. A. W. GRABAU. Guide to the Geology and Paleontology of Niagara Falls and Vicinity, Bull. N. Y. State Mus., vol. 9, No. 45, 1901, pp. 1-85, pls. 1-11. J. W. SPENCER. The Falls of Niagara, etc. Dept. of Mines, Geol. Surv. Branch, Canada, 1907, pp. 490, pls. 43. G. K. GILBERT. Rate of Recession of Niagara Falls, etc. Bull. 306, U. S. Geol. Surv., 1907, pp. 31, pls. 11. G. DE GEER. Quaternary Sea Bottoms of Western Sweden. Paper 23, Livret Guide Cong. Géol. Intern., 1910, pp. 57, pls. 3. CHAPTER XXVI LAND SCULPTURE BY MOUNTAIN GLACIERS =Contrasted sculpturing of continental and mountain glaciers.=—In discussing in a previous chapter the rock pavement lately uncovered by the Greenland glacier, we learned that this surface had been lowered by the processes of plucking and abrasion, the combined effect of which is always to reduce the irregularities of the surface, soften its outlines, and from sharply projecting masses to develop rounded shoulders of rock—_roches moutonnées_.