SCIENCE. 



629 



areas generally ) approach or even reach the surface to- 

 ward the southern limit of ice-action, as in southern Indi- 

 ana, 6 ' 2 Illinois, 63 Iowa, 64 and Nebraska, 65 and in northern 

 Missouri, 66 the second statement must be viewed in a sim- 

 ilar light. 



P. 170. — The cave-fauna, especially in Europe, is es- 

 sentially identical with that commonly regarded as Qua- 

 ternary or Champlain ; and as already intimated, there is 

 good reason to suspect that this fauna was at least parti- 

 ally pre-glacial. Moreover, the same facts relied on by 

 the elder Buckland to establish the anti-diluvian age of 

 the ossiferous cave-deposits, 61 must today be considered 

 equally conclusive of the pre-glacial existence of these 

 remains. 



On passing to a more general surrey of the work there 

 is found to be less occasion for criticism, and indeed some 

 grounds for high commendation. Thus, the influence of 

 aqueous vapor and other substances diffused in the atmos- 

 phere upon terrestrial temperature is rarely lost sight of, 

 the existing glaciers are faithfully and accurately described, 

 and the general character and effects of Quaternary gla- 

 ciation are fully and clearly dealt with. The teachings 

 as regards the recurrence of glacial epochs and their 

 influence upon the successive geological formations of the 

 globe are, however intensely radical. The evidence relied 

 on to demonstrate the glacial origin of sandstones and 

 conglomerates, azoic shales and slates, and unoxidized 

 argillaceous rocks generally, is quite inadequate. For 

 instance, the idea that the iron of glacial mud alone is 

 normally unoxidized while that of river silts is normally 

 oxidized, appears to be expressly contradicted by the facts 

 that the iron of the Lors (which is almost certainly 

 formed of impalpable glacial debris ), is nearly universally 

 peroxide, even when the deposit is one or two hundred 

 feet thick, while that of the post Lors alluvium of the 

 lower Mississippi is invariably protoxide, even within a few 

 feet or even inches from the surface ; and the opinion 

 that paleozoic ice-action cannot be proven by the same 

 evidence as that attesting Quaternary glaciation is directly 

 opposed by the facts that the Talchir ( lowest paleozoic) 

 beds of Peninsular India contain striated and polished 

 boulders imbedded in the finest silt, and that the under- 

 lying Vindhyau (azoic) rocks bear similar markings; 

 though even in this case the original observers do not re- 

 fer the phenomena, with any degree' of certainty, to gla- 

 cial action. Again, while the discussion of glacial hypo- 

 theses and theories of glacial movement is tolerably full 

 and ( unless possibly in a single instance ) eminently im- 

 partial and candid, the " composite theories " adopted are 

 quite valueless, since the detailed investigation given to 

 the subjects is in almost every case much less searching 

 and exhaustive than that upon which each hypothesis was 

 originally based. It may be questioned, indeed, whether 

 the method of throwing together a number of essentially 

 distinct and imperfectly weighed hypotheses, and taking 

 the sum or the mean of all as the only consistent theory, 

 will ever come into general repute, however strongly it 

 may be supported by a confusing array of glittering gen- 



42 Primitive Industry,'' Abbott, 1881, pp. 541, 551. 



43 14th Ann. Rep., Peabody Museum, 1881, p. 23. 



44 Am. Jour. Set., vol. XXII, 1881, p. 402. 



45 " Forms of Water," pp. 155-7. 



48 Edin. New Phil. Jowtt., Jan. 1842 ; " Occasional Papers on the The- 

 ory of Glaciers," 1859, p. 3. 



47 Edin. N. P. J., Oct., 1842 ; Occ. Papers, p. 9. 



48 Occ. Papers, p. 10. 



45 " The solution of this important problem [ the theory of glacier mo- 

 tion], would be obtained by the correct measurement, at successive peri- 

 ods, of the spaces between points marked on insulated boulders on the 

 glacier ; or between the heads of pegs of considerable length, stuck into 

 the matter of the ice, and by the determination of their annual progress." 

 Op. cit.y p. 77 ; Occ. Papers, p. 10. 



60 " Manual of Geology," 1880, p. 694. 



51 " Principles of Geology," revised ed., 1854, p. 224, note. 



52 Occ. Papers, pp. 03, 269. 



63 Geol. Mag., vol. Ill, p. 493. 



eralities. Thus, with regard to the problem of ice-motion; 

 it is of course true that the dilatation, fracture-and-vege- 

 tation, and pressure-melting hypotheses are based on the 

 observed behavior of ice ; but it does not necessarily fol- 

 low that these properties, either individually or collect- 

 ively, produce the phenomenon of flowing in large bodies 

 of ice. To illustrate :— solids generally expand and con- 

 tract with alterations in temperature ; they may be frac- 

 tured by irregular strain or impact ; they may be united 

 into homogeneous bodies by pressure as shown by Spring ; 

 and those which expand on solidifying may be melted by 

 pressure ; yet no physicist attributes the flow of solids 

 ( which has been investigated by Tresca, Roberts, Ware, 

 and others ) to any or all of these properties. Finally, 

 there are important omissions, notably with respect to 

 the widespread hipartite structure of the drift in many if 

 not most glaciated regions, which has led many Euro- 

 pean and several American geologists to conclude that it 

 was formed during two distinct periods, separated by a 

 considerable era of mild climate. The general neglect 

 of the results of American (and indeed Foreign) study 

 has been incidentally noted in preceding paragraphs. 



The illustrations, which are of the finest character and 

 elaborately described, are mainly reproduced from pho- 

 tographs of existing glaciers and of interesting phases of 

 glacial phenomena in America and elsewhere. They are 

 of course open to the objection which may be urged 

 against all photographs of natural scenery — i. e., that the 

 most instructive and valuable details are often obscured 

 or concealed ; — though many of the plates are cf remark- 

 able clearness and beauty. The illustrations are not, how- 

 ever, superior or even quite equal to many which have al- 

 ready been published by Agassiz ( for instance, in the at- 

 las accompanying "Etudes sur les Glaciers;" Neuchatel, 

 1840 — " Untersuchungen tiber die Gletcher," Solothurn, 

 1841 ), and others. 



It should be added that the necessity for all the fore- 

 going criticisms appears to have arisen from the peculiar 

 design of the work and the circumstances under which 

 it was prepared. The authors explain in the preface that 

 in order to meet the agreement with the publishers, it was 

 necessary to prepare the text with far greater haste than 

 was desirable ; and remark that, — " if the reader will 

 consider that the main object in the book is not to afford 

 a complete history of glaciation, but to present a body of 

 graphic illustrations of glacial phenomena, and that the 

 text is designedly subordinate to this purpose, he will 

 then better understand the apparent short-comings of the 

 work." 



Viewed as a whole, it appears that the work describes 

 no new phenomena and presents no new theoretical views, 

 while it exhibits many deficiencies and inaccuracies. It 

 cannot therefore be regarded as in any sense a valuable 

 contribution to the subject dealt with, or even as a satis- 

 factory exposition of the present state of that subject. 

 To the working student it will accordingly be worse than 

 useless, since it will impose upon him a heavy financial and 



54 " A Criticism of Dr. CrollYMolecular Theory of Glacier Motion," 

 London, 1880. 



65 " Systematic Geology " of the Fortieth Parallel Survey, 1878, pp. 

 447-8. 



68 Geol. Surv. O., vol. Ill, pt. I, 1S78, p. 38, et passim . 



67 Am. Jour. .V/., vol. XV, 1878, p. 339 ; Proc.A. A. A. 5\, vol. XX- 

 VII, 1878, p. 198 ; Geol. Mag., vol. VI, 1879, pp. 353, 412. 



58 Phys. Geol. and Geog. of Neb., 1880, p. 259. 



68 Geol. N. H., vol. Ill, 1878, p.333. 



80 Proc. A. A. A. S., vol. XXVIII, 1879, p. 350. 



81 Mem. Cour. ct Mem. des Sar. Entr. of the Acad. Roy. de Belgian*. 

 vol. XLIV, 1881. Noticed in Am. Jour. Sci., vol. XXII, 1881, p. 80. 



62 Geol. Surv. Ind., 1872. n. 404 ; 1875, p. 171 ; and elsewhere. 



63 Geo. Surv. Ills., vol. Ill, 1868, p. 190; IV, 1870, p. 194 and elsewhere. 



84 Geol. Iowa, 1870, vol. I, p. 327 ; 1 1, p. 9 ; and elsewhere. 



85 Geol. Surv. Mo., 1855-71, p. 162 ; 1873-4. P- *45 ; and elsewhere. 



88 Phys., Geog. and Geol. Heb., 1880, p. 254.— In each of the first four 

 States above mentioned, the occurrence of the clay and its stratigraphical 

 position has been determined mainly by personal observation. 



87 "Reliquiae Dilunanae." 1824, pp. 48-51, 171-84. 



