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Notices respecting New Books. 





Gneiss ; ' may have been associated with " the earliest solar tidal 

 waves, and the more pronounced foliation of the Archaean schists 

 with the subsequent lunar tidal waves of the magma." .... 

 " Then as now the tidal action would vary (within much wider 

 limits, however) with the relative positions of the Sun, the Earth, 

 and the Moon, the maximum effect being produced when the 

 Moon was in 'meridian.' Pfaff (Algem. Geol. ate. ex. Wiss. p. 1 88 et 

 seq.) has discussed the action of tidal movements in the magma 

 upon the earliest rind of the Earth, initiating the first permanent 

 inequalities upon its surface. If the Archaean schists (taken as a 

 whole) represent this first-formed rind, their materials as they 

 accumulated by precipitation from the heavy atmosphere being bathed 

 through and through with H 2 in a highly superheated condition, 

 we seem to have at once an explanation both of the frequent 

 recurrence of gneiss (in a subordinate degree) among the schists as 

 a result of tidal movements, and of those lithological characters by 

 which they have misled the Keptunists into regarding them ' as 

 sediments.' " The author takes his favourite subject of glacier- 

 ice as an example of the several results of the physical forces act- 

 ing on such a magma. 



IV. Hyperphoric change is illustrated by dolomitization, some 

 amygdaloids, some masses of rock-salt, and the production of 

 selenite from pyrites in fossiliferous clays. 



V. Contact-metamorphism, combining par amorphic, metatropic, 

 metataxic, and hyperphoric changes, is treated in stages— 1. Direct 

 effects of heat and pressure. 2. Effects of the circulation of 

 superheated water between the intrusive mass and the adjacent 

 rocks. 3. Changes following upon the cooling of the igneous 

 intrusive mass. 



The General Remarks treat of the meaning and application of 

 several words relating to metamorphism and metaphoric rocks, — 

 such words and applications as the author would or would riot 

 approve of ; also of Archaean, Cambrian, and some other old rock- 

 stages. In his Conclusions he insists on the complex nature of 

 metamorphism, and the different processes by which the results 

 are effected ; — on the incomplete explanation hitherto given of 

 " regional metamorphism ;" — that " unrformitarianism" really ought 

 only to apply to the fact of the Earth having always been subject 

 to the same universal laws as the other cosmical bodies ; — and that 

 the mass of the Earth and its Atmosphere has remained the same 

 from the beginning. He accepts the theory that there was a 

 pre-oceanic stage, and that the Archaean gneisses and schists were 

 essentially diagenetic, rather than metamorphic ; and warns us that 

 " such phrases as ' the highly metamorphised Archaean gneisses and 

 schists ' must be relegated to an obsolete nomenclature of geological 

 science." The author winds up his Conclusions by stating that 

 " as the mists and clouds thus diperse, our intellectual vision begins 

 to descry a boundary to geologic time, and the physical geologist 

 begins to feel that over this question he can join hands with the 

 astronomer and the natural philosopher." 



