SCIENCE. 



627 



ological time, is fully established ; and they certainly do 

 not regard the covering by ice of " a very large part of 

 land and sea " as a " fact," or indeed as more than an 

 extremely vague hypothesis. 



P. 40. — Croll long since suggested 5 that Caithness and 

 the Orkneys were glaciated by the Scandinavian ice-sheet, 

 and Peach and Home have recently urged 6 that during 

 a part of the glacial period the Shetlands were overspread 

 by the Scandinavian mer de %/ace, while during another 

 part they gave origin to a system of local glaciers, though 

 Milne-Home 1 seriously questions these several conclu- 

 sions ; and it has also been suggested by Reid, 8 though it 

 can hardly be regarded as established, that the contortion 

 of the drift along the Norwich coast was effected by Scan- 

 dinavian land-ice. As shown by Croll's 9 and Geikie's, 10 as 

 well as all other reliable maps, however, all the British 

 highlands were unquestionably independent centers of 

 glaciation, quite distinct from the Scandinavian ice-sheet ; 

 — indeed, when Milne-Home characterized the statement 

 that " the land-ice which glaciated Scotland could only 

 have come from Scandinavia " as an " astounding declara- 

 tion," 11 Peach and Home hastened to explain that the 

 word Scotland was a mis-print for Shetland}* There 

 are also grave reasons to question whether a polar ice- 

 cap ever existed in the northern hemisphere, as the writer 

 has endeavored to prove, 13 and it is quite certain that if 

 such an ice-cap did exist it did not extend to the British 

 Isles by way of Scandinavia. So long ago as 1845 

 Murchison showed by means of a map in his " Geology of 

 Russia and the Ural Mountains," that the Scandinavian 

 drift " proceeded eccentrically from a common centre ;" 14 

 and Geikie (illustrating his remarks by a map) says : 

 " the direction of the glaciation in the extreme north of 

 Scandinavia, the peninsula of Kola, and north-eastern 

 Finland, demonstrates that the great mer de glace 

 radiated outwards from the high grounds of Norway and 

 Sweden, flowing north and northeast into the Arctic 

 Ocean and east into the White Sea, and thus clearly 

 proving [proves ?] that northern Europe was not over- 

 flowed by a vast ice-cap creeping outwards from the 

 North Pole, as some geologists have supposed." 15 



Pp. 41,44. — It is not known that a continuous ice-front 

 ever stretched across the American continent, since a 

 portion of the region eastward of the Cordilleras remains 

 unexplored. Dana remarks, " since evidence of the great 

 southward moving glacier fail over the region west of a 

 line parsing from a few degrees west of Winnipeg, south- 

 eastward through Western Minnesota and Iowa, near the 

 meridians of 98°-ioo°, and all the way westward to the 

 borders of California and Oregon if not to the Pacific 

 coast, the ice thinned out toward the interior of the conti- 

 nent and was mostly absent except about the higher parts 

 of the Rocky Mountains." 16 There is moreover no suffi- 

 cient reason for believing that the American ice-sheet 

 swept down from polar regions. Hitchcock's map of 

 directions of ice-flow, which is reproduced in the work 

 under consideration (following pi. XX.), indicates that the 

 principal American center of dispersion was probably in 

 the northern Laurentian Highlands ; — a view which is 

 corroborated by more recent observations of the Canadian 

 Geological Survey. 11 Houghton has also shown that the 

 boulders of the Arctic archipelago were carried north- 

 ward. 18 



s Geol. Mag. May and June, 1870; "Climate and Time,'' chap. 

 XXVII. 



'Qiiar. Journ. Geo!. Sac, vol. XXXV, p. 778 ; Geo/. Mag., II., vol. 

 VIII, p. 65 ; ibid, p. 364. 



''Trans. Edin. Geo!. Soc. vol. III. pt. 3, p. 357 ; Geol. Mag., II., vol. 

 VIII., p. 205 ; ibid, p. 44g. 



a Geoi. Mag., II, vol. VII, p. (A number ol the writer's volumes are 



in the bindery at this writing, and a few references accordingly cannot 

 be given in full.) 



*" Climate and Time," p. 44a. 



10 Accompanying 11 Great Ice Age." 



"Q. J. G. S., XXXV, p. 809. 



™Geol. Mag., VIII, p. 69. 



P. 42.— The quoted remarks describing the southern 

 limit of ice-action in the Mississippi valley display un- 

 pardonable disregard of the work of Cox and Collett in 

 Indiana, of Worthen and his associates in Illinois, of 

 the several Missouri geologists, of White and St. John in 

 Iowa, of Aughey in Nebraska, of N. H. Winchell and 

 Upham in Minnesota, and even of Hitchcock's map ap- 

 pearing in the volume. The southern limit of the drift 

 does not pass through either Iowa or Minnesota, but 

 through southern Indiana and Illinois, northern-central 

 Missouri, and Nebraska. The statement possibly origi- 

 nated in confounding the great Kettle Moraine with the 

 southern drift-line, though as specifically pointed out by 

 Upham, 19 and hardly less distinctly by Chamberlin, 20 these 

 lines are 300 miles apart. 



The glacial phenomena of south-western British Amer- 

 ica have been carefully and tolerably fully studied by G. 

 M. Dawson.' 21 



Pp. 66, 68. — An explanation of the origin of kames 

 and aasor which is satisfactory to students ot glacial phe- 

 nomena was independently offered by N. H. Win- 

 chell, 22 Hoist, 23 and Upham. 24 The hypothesis is as defi- 

 nite and probable as almost any other portion of the gla- 

 cif 1 theory. 



Pp. 70, 90. — Tyndall has shown" that a diminution of 

 terrestrial temperature could never inaugurate a glacial 

 epoch ; it has never been demonstrated that augmenta- 

 tion of temperature would be in any degree likely to pro- 

 duce a similar effect ; and, accordingly, Poisson's and 

 Le Coq's hypotheses can hardly be regarded as "reason- 

 able " or " likely " in the present state of knowledge. As 

 Croll has urged 26 , there are grave reasons for questioning 

 whether anything like half of the heat reaching the earth 

 comes from the stars. 



P. 75.- — Loomis, describing the orbital motion of planets 

 undisturbed by exterior forces, says : " the curve cannot 

 be a circle unless the body be projected in a [particular] 

 direction * * *, and, moreover, unless the velocity 

 * * * is neither greater or less than one particular 

 velocity;" 21 and Stockwell, speaking of the solar system 

 in its actual condition, says : " the eccentricity of the 

 earth's orbit will always be included within the limits of 

 o and 0.0693888. " 28 * 



P. 95. — Sound bases for the assertion do not sppear. 

 Hilgard says 29 : " the relations mentioned by Tuomey 

 (Second Report on the Geology of Alabama, p. 146) 

 as existing between the shore of the Tertiary sea and the 

 region of occurrence of the southern [northern ?] drift on 

 the Atlantic slope, are not so clearly recognizable in 

 Mississippi and Alabama ;" and further westward no re- 

 lation whatever is apparent. Furthermore the "northern 

 drift " of Hilgard and Tuomey was deposited far beyond 

 the southern limit of the ice. 



P. 107. — Le Conte shows graphically 30 that, admitting 

 the influence of eccentricity, glaciation would only be pos- 

 sible after protracted secular refrigeration. The period 

 in which this refrigeration reached such a degree as to 

 permit of glaciation has not been determined. If in the 

 Cambrian, Le Conte's diagram is, of course, incorrect ; 

 but it is not seriously maintained by working geologists 

 in America that such was the case. Speaking of the 

 Quaternary Le Conte, referring to Nordenskjold's ob- 

 servations, 31 declares 3 '- : " that glacial conditions were 



™Proc. A A. A. S., vol. XXIX, p . 



14 Cited by Lyell, " Antiquity of Man," 4th revised ed., 1873, p. 275, 

 note. 



15 " Great Ice Age," p. 354. 



""Manual of Geology," 3d. ed. 1880, p. 537. 



"Geol. Surv. Con. Rep. Frog, for , p ; ibid, tor , p . 



18 McClintock's " In the Arctic Seas," author's ed., appendix, p. ^368. 

 1!1 8th Ann. Rep. Geol. and Nat. Hist. Surv. Minn., r p. 73. 

 |°Geol. Wis., vol. ii., 1877, pp. 205-15; Trans. Wis. Acad, of Arts, 

 Sciences, and Letters, vol. — , p. — . 



™Quar. Jour. Geol. See,, vol. xxxiv,, pt. 1; Geol. Surv. Con., Rep. 

 Prog, for — , p. — ; ibid, for — , p. — . 

 n Prec.A. A.A.S., vol. — , p. — . 



