628 



SCIENCE. 



ever before reached, even in polar regions, seems more 

 than doubtful." 



The foundation for the second statement quoted does 

 not appear. 



P. 108. — It has not been empirically established that 

 the effect of fog-banks is to diminish temperature ; 

 and analogy with the known observation of finely dis- 

 seminated water suggests that a directly opposite result 

 ought to be produced. Croll's argument has been con- 

 sidered by Newcomb 33 and the writer. 34 



P. 113. — G. M. Dawson 35 has investigated the late-Qua- 

 ternary depression of Vancouver's Island and British 

 Columbia, and finds it to have been practically commen- 

 surate with that of the Atlantic coast. 



P. 119. — Geologists are not united as to the age of the 

 great pachyderms. Thus, Collett 36 records observations 

 indicating that they were recent ; while Phillips 31 and God- 

 win- Austen 38 regarded them as wholly pre-glacial, and 

 Hall 39 and Belt 4 " have shown that at least some individu- 

 als existed before the advent of the ice. 



PP. 119-20. — Howorth has recently (mainly since the 

 publication of " Glaciers ") examined the evidence relat- 

 ing to the former existence of the mammoth in Siberia, 

 and reaches the conclusion (among others). 1st, that 

 the animals lived where their remains now lie ; and 2nd, 

 that the climate was comparatively mild at that period 41 . 



P. 134 A subsequent and apparently complete study 

 of the locality by Lewis leads to the conclusions; 1st, 

 that the implements are confined to the Trenton River 

 gravel : and 2nd, that this gravel was deposited " at a 

 period immediately following the last glacial epoch." 42 . 

 If, as suggested by F. W. Putnam, 43 the flints were drop- 

 ped into this gravel while in process of formation by the 

 paleolithic men who hunted and fished along the old river- 

 bluffs of New Jersey, it follows that these men were post- 

 glacial ; and even if the correctness of Lewis's views are 

 not fully established, as intimated by Dana, 44 this instance 

 does not demonstrate, or even indicate, man's pre-glacial 

 existence. 



P. 140. — Tyndall mentions 45 that Scheuchter first pro- 

 pounded the dilatation theory in 1 705, that in 1 760, or nearly 

 forty years in advance of De Saussure, Altman and Grii- 

 ner enunciated the sliding theory, and that in 1773, or 

 thirty years before the publication of De Saussure's 

 "Voyages dans les Alpes," the plastic theory was put 

 forth by Bordier. 



P. 142. — The re-opening, not incidentally or even judi- 

 cially, but in a ludicrously partisan .tone, of this now al- 

 most forgotten though erstwhile bitter controversy, would 

 be quite unjustifiable even if the statements where not 

 erroneous. Forbes' first visit to the alpine glaciers (as 

 published by himself in that year), was on the 9th. of 

 August, 1841 ; 46 during which visit he was in the com- 

 pany of Agassiz. Throughout this season his observa- 

 tions, as indicated by his published results, were confined 

 to superficial phenomena; chiefly " ribboned structure" 

 and '• slaty cleavage." On the 24th of June, 1842, he 

 again reached Montannent 41 with a set of instru- 

 ments of precision, avowedly and obviously carried thither 

 for the express purpose o! instituting a series of measure- 

 ments of the motion of the ice — the necessity for such 

 measurements having been pointed out hi lectures in De- 

 cember, 1 841, and January, 1842, 48 and also in the Edin- 



' i3 Geol. Fdren. Stockholm /-«>-/(., Bd. iii., No. 3, pp. 97-112. 



,i A>n. Jour. Set'., Lee, 1877 ; I'roc. A. A. A. S., vol. xxv., /. 216, el 

 req.: and vol. iii. of the late New Hampshire reports. 



Heat as a Mode of Motion," Am. ed., p. 176 ; " Forms of Water,' 

 P- *54- 



w " Climate and Time," p. 39. Newcomb says (Am. Jouru, Set., Vol. 

 XI. ,1876, p. 263)— " Practically there is but one source from which the 

 surface of the earth receives heat, the sun, since the quantity received 

 from' all other sources is quite insignificant in comparison." 



57 " Treatise on Astronomy," 1876, p. 138. 



n " Secular Variations of the Orbits of the Eight Principal Planets." 



Smithsonian Contributions, No. 252, 1872, p. XI. 

 '■"Geol. and Agricult. Miss., i860, p. 28. 

 " Elements of Gcolo " 1879, p. 550. 



burg- Review for April, 1842 49 ;— and the " First Letter on 

 Glaciers," containing the " account of the first experi- 

 ments, undertaken in June, 1842, to determine the laws 

 of motion of the Mer de Glace of Chamouni " (published 

 in October as already noted ), was dated "4th July, 1842" ; 

 on which very day as stated by Dana on Tyndall's au- 

 thority, 50 Agassiz' measurements proving the more rapid 

 flow of the medial portion of the glacier, were published 

 in the Comptes Hindus. Lyell, speaking of the more 

 rapid medial than lateral motion of glaciers, says 51 ; 

 Mr. Agassiz, at p. 462 [of the " Systeme Glaciere "], 

 states that he published in the Deutche Vierteljahrschrift 

 for 1841, this result as to the central motion being greater 

 than that of the sides, and was, therefore, the first to cor- 

 rect his own previous mistake. " Comment is unneces- 

 sary. 



Pp. 143-4. — Substances not previously regarded as vis- 

 cous, as for instance Stockholm pitch " so hard as to be 

 fragile throughout, and present angular fragments with a 

 conchoidal fracture " and a glassy lustre 52 , are also re- 

 ferred to by Forbes. 



The " followers " who hold the view indicated are not 

 advocates of the viscous theory proper, which is essenti- 

 ally molecular. The motion of viscous, as of fluid bodies, 

 may, however, be very imperfectly illustrated by the 

 movement of a heap of independent spherical masses. 



P. 145. — The re-statement of this view, which it is 

 painful for admirers of Croll's important labors in other 

 directions to discuss, is hardly excusable. Readers may 

 satisfy themselves as to its validity by referring to the 

 criticisms of Blakie 53 and Teal 54 . The authors should 

 have pointed out the differences between solid, liquid, and 

 gaseous molecules of EL O. 



P. 148. — The motion of the alternately freezing and 

 thawing snow unquestionably occurred in the manner as- 

 sumed in the dilatation theory as advocated by Scheuchzer, 

 Charpeutier, and, especially Mosely ; but it is just as un- 

 questionably distinct from the true flow of glacier ice. 

 The recognition of miniature glaciers in the New England 

 snows, tar transcends the peculiar ideas of Muir, which 

 are so strongly deprecated by King 55 . 



Pp. 151, 154, 159. — The extraordinary conclusions 

 reached are perhaps to be attributed to the inadequacy of 

 the theory of glacier motion adopted. The statements 

 may be looked upon as representing unduly emphasized 

 ideas of a purely speculative nature. 



P. 165. — So long as a majority of leading students of 

 Quaternary phenomena classify the upper and generally 

 yellowish portion and the lower and generally bluish por- 

 tion of the drift respectively as Upper Till and Lower 

 Till, and look upon them as distinct in either time or mode 

 of formation, as do Newberry, Upham, Hitchcock, 

 Aughey, N. H. Winchell, Stone, and many others in the 

 United States, and so long as these deposits are distinctly 

 separated by a characteristic vegetal stratum, as they are 

 at least in southern Ohio, 56 northeastern Iowa, 51 and Ne- 

 braska. 58 the first quoted statement must be regarded as 

 unsupported by facts, notwithstanding the possibility that 

 atmospheric and vegetal action might, as urged by 

 Hawes, 59 Julien, 60 and Van den Brock, 61 produce a similar 

 discoloration of a single homogeneous formation having 

 the constitution of the Lower Till ; and since the bluish 

 clays quite frequently (and indeed over some considerable 



31 Geol. Mag,, Nov., 1875, p. 525. 



32 " Elements," p. 549. 



33 A in. Jour. Set., vol. xi, 1876, p. 272. 



34 Popular Science Monthly , vol. xvi, 1880, p. 816. 



36 Vide, note 21. 



Ind. Rep. of the Bureau of Statistics and Geol., 1880, pp. 384-6. 



37 " Geology of Yorkshire," 1829, vol. I, pp. 18, 52. cited by Belt, infra. 

 3(1 Reports British Assn., 1863, p. 68. 



39 21st. Regent's Rep. on N. Y. State Cabinet, 1871, p. 103, el req. 



"' Popular Science Monthly, vcl. XII, 1878, p. 62. 



41 In an unfinished scries of papers in vols. VII. and VIII, of the Geol. 



Mag. 



