NA TURE 



49 



ROCK METAMORPHISM. 

 Chemical and Physical Studies in the Metamorphism of 

 Rocks, based on the Thesis written for the D.Sc. Degree 

 in the University of London, 1 888. By the Rev. A. 

 Irving, D.Sc.Lond., B.A., F.G.S. (London: Longmans, 

 Green, and Co. 1889.) 



DR. IRVING is well known as a writer on Bagshot 

 beds. He appears in a new light as the pro- 

 pounder of theories dealing with the metamorphism of 

 rocks. His ideas on this subject are classified under 

 three heads : paramorphism, metatropy, and metataxis. 

 Paramorphisni, according to the author, includes those 

 ^changes within in the rock-mass, involving changes in the 

 chemical composition of the original minerals and the 

 formation of new minerals ; metatropy denotes changes 

 in the physical character of rock-masses ; and metataxis, 

 mechanical changes, such as the development of cleavage. 

 Changes brought about by the introduction of a new, or 

 the removal of an old mineral {e.g. dolomitization) are 

 treated under the head of hyperphoric change. 



The author writes, he tells us, for those who are willing 

 :o look at geological phenomena " in the light of physical 

 ind chemical ideas." To all others his dissertation 

 ■ must read rather like romance than sober science." 

 1 Ic is not far wrong when he complains that the chemical 

 mlIc of geology has been neglected since the time of 

 r.iscliof. The reason for this is to be found in the fact 

 hat geologists have been too busily engaged in reaping 

 golden harvests in the demesnes of palaeontology and 

 stratigraphy to be much tempted by the allurements of 

 :hemical geology. With the resuscitation of petrology, 

 lowever, the chemical constitution of rocks begins again 



present problems of great interest and importance. 

 '■ 't the author turns his chemical knowledge to bad 



unt, we think, in applying it to the elaboration of 

 M eping generalizations. The views he puts forward 

 nay or may not be founded on sound chemical and 

 )hysical axioms ; but mere test-tube reactions will not 

 uftice to explain the operations of Nature in the vast 

 iboratory of the universe. The phenomena of meta- 

 iKirphism represent the net result of numerous and often 

 antagonistic forces ; and are not always simple reactions 

 hat may be expressed by a neat chemical equation. 



Dr. Irving appears to be highly gifted with what he 

 cniis a "scientific imagination," the meteoric flights of 

 vhich carry him far above the solid |;round of fact or 

 ;vcn justifiable theory. An instance of this faculty of the 

 uithor's will be found on p. 66, where he seeks to explain 

 he origin of foliation in Archaean rocks by the influence 

 >f " solar and lunar tides upon the non-consolidated 

 niL^ma in the Archaean and pre- Archaean {sic) stages of the 

 11 th's evolution." He proceeds : — 



'■ In such an unequally viscous mass there would be 

 ion, contortion, and shearing to any extent during 

 idal pulsations which the magma was suffering. . . . 



I lions already solidified, or nearly so, by segregation 



1 otherwise, as time went on, would by their vis inerticE 

 ncsent obstacles around which a fluxion structure would 

 e\ clop itself in the contiguous portions of the yielding 

 la^^ma, giving us perhaps in some cases ' Augengneiss.' 

 he local tension of parts of the viscous lithosphere, 



Vol. xli. — No. 1047. 



especially near the crests of the waves, would imply 

 stretching and consequent lowering of temperature, a 

 circumstance favourable to local solidification. Who 

 shall say that in the later and feebler struggles of this 

 kind, as secular cooling went on, and the magma 

 approached nearer and nearer to the conditions required 

 for consolidation, some of these tidal waves may not 

 have become in situ sufficiently rigid to outline some 

 of the earliest lines of elevation ? " 



This is speculative enough in all conscience. On 

 p. 29, the author discusses the influence of the salts 

 dissolved in sea-water on submarine lava-flows, and 

 suggests that serpentinization and the conversion of 

 orthoclase into albite are the result of some process of 

 " submarine paramorphism " effected by this agency. 

 This, again, is pure hypothesis, there being no facts to 

 support such a view. 



There is a flavour of pedantry in the use of such 

 expressions as " burnt hydrogen " for water (p. 64), or in 

 such sentences as " orthoclase is probably the embryonic 

 silicate of the terrestrial lithosphere" (p. 67). As the old 

 lady is said to have remarked of the word Mesopotamia, 

 there is something especially comforting and satisfying 

 about this last sentence. 



The pages bristle with " hard words," some of which 

 are new to science. "Vitreosity" has an uncanny 

 sound ; " apophytic " is curious ; and " dehydrodevitrifica- 

 tion " is as inelegant as it is long. Indeed, so technical is 

 the author's language that a clear understanding of his 

 meaning involves constant reference to his definitions. 

 Unfortunately such reference is rendered impracticable 

 by the absence of an index. 



The book bears witness to Dr. Irving's extensive 

 acquaintance with foreign chemical and geological 

 literature ; references to foreign sources being abundant, 

 sometimes superfluous. Indeed, there is more evidence 

 of the author's acquaintance with literature than with 

 facts derived from original observation. Good ideas 

 may here and there be picked out ; and the work no 

 doubt contains some plausible explanations of geological 

 phenomena ; but of this we are assured, that the science 

 of geology will not be advanced by those who spend 

 their time in manufacturing wide-reaching generaliza- 

 tions or attractive theories in the library, but rather by 

 those who are content to labour, with the hammer in the 

 field, the microscope in the cabinet, and the balance 

 in the laboratory at the ofttimes wearisome task of 

 unravelling details. 



This book may be placed in the same category as 

 Sterry Hunt's " Chemical and Geological Essays." Such 

 books can be recommended to those with a taste for 

 speculation and rumination. To others they may be 

 productive of mental confusion and headache. 



HAND-BOOK OF DESCRIPTIVE AND 

 PRACTICAL ASTRONOMY. 

 Hand-book of Descriptive and Practical Astronomy. By 

 G. F. Chambers, F.R.A.S. Part I. The Sun, Planets, 

 and Comets. (Oxford: Clarendon Press, 1889.) 



THE avowed aim of the author of this work, since the 

 publication of the first edition in 1861, has been to 

 keep its pages up to date— to make it a sort of vade 

 mecuvi to astronomers ; and, regarded as a book en- 



D 



