[122] In a letter to Mr. Bunbury, dated November 13th, 1854 (Life, Letters, and Journals, vol. ii. p. 199). It is written from 53, Harley Street, one in the previous August bearing the superscription of 11, Harley Street, so that he appears (though there is no allusion to this in his published letters or journals) to have removed into another house in the same street. The number of this was subsequently altered. [123] Another letter to Mr. Bunbury, dated April 30th, 1856 (_ibid._, p. 212). [124] This deposit belongs to the Tertiary era (Oligocene system). [125] Life, Letters, and Journals, ii. p. 243. [126] The largest, called the Zwerglithurn, is about one and a half hours walk above Viesch. [127] This had been asserted in support of the hypothesis of "craters of elevation." [128] Colonel Lyell had retired from the army and returned to England a short time before the outbreak of the Indian Mutiny. [129] _See_ Professor J. W. Judd: "Volcanoes" (International Scientific Series), Fig. 22. [130] In the famous eruption of A.D. 79. [131] A volcano of Japan. [132] These results are worked into the tenth edition of the "Principles" (chaps. xxv. and xxvi.). _See also_ a paper on Stony Lava on Steep Slopes of Etna (Proc. Roy. Soc. 1858, ix. p. 248). He received the Copley Medal from the Royal Society in November. CHAPTER X. THE ANTIQUITY OF MAN. Though many men on reaching their sixty-third year are content to rest upon their oars and not to attempt new ventures, Lyell had plunged into a question which was arousing almost as much excitement as the origin of species--namely, the antiquity of man. It was a question, indeed, which for a long time must have been before his mind--witness his remarks on Dr. Schmerling's work in the caves near Liége; but it had assumed a special significance owing to the famous discovery of flint implements in the valley of the Somme.[133] The whole subject also would have a special interest for Lyell, because he had made Tertiary deposits his special field in stratigraphy, and had worked at this subject downwards, comparing extinct with living forms, so that he had seen more than others of the borderland which blends by an insensible transition the province of the geologist with that of the archæologist. Probably also the thought which he had been giving to the question of the origin of species would bring into no less vivid prominence that of the age and origin of the human race. Be this as it may, he undertook a task comparatively novel, and for the next three years was fully occupied in the preparation of his third great book, "The Antiquity of Man." Travel was necessary for this purpose also; but as the journeys were less lengthy than those already described, and led him for the most part over old ground, it is needless to enter into details. He visited the gravels of the Somme Valley and the caves on the Meuse, besides other parts of Northern France and Belgium,[134] the gravel pits near Bedford, and