136 TERTIARY ROCKS OF AUSTRALASIA, 



destroyed a ricli vegetation in the vicinity of Mount 

 Tarawera in New Zealand. 



Although from the evolutionist's point of view it would 

 be unreasonable to look for a break or hiatus in the 

 continuity of physical and organic processes connected 

 with the succession of rocks and organic life as regards 

 the whole globe, still it must be borne in mind, in respect 

 of any one region, that breaks of a very remarkable 

 character do occur ; and although evidences are becoming 

 more and more abundant that the local break involves 

 merely a shift of the conditions to other regions where the 

 threads of continuity are maintained, yet such is the 

 obscurity caused by our ignorance of the direction, extent, 

 and exact sequence of these local shifts, and such are the 

 complications brought about by the commingling of 

 migratory forms from different sources in the successive 

 provinces invaded, that we are still involved in much con- 

 fusion respecting the true sequence of the rocks and 

 organisms of different regions. 



This confusion is intensified by the general tendency 

 among geologists, in widely separated provinces, and, 

 indeed, in opposite hemispheres, to aim at fixing parallel 

 limits too closely, — not only with the great systematic 

 divisions of Europe, where the sequence and boundaries of 

 rock systems were first closely studied, but also with a 

 definite number of minor subdivisions which strictly can 

 only be of local value. Whereas, if due regard be paid to 

 questions concerning unbroken continuity of laws or forces 

 in operation*, and the inevitable constant successive inter- 

 weaving of organisms in different regions from many 

 independent centres of origin, forming new groups of asso- 

 ciation, we should be led to expect that the slow spread of 



* " As all the living forms of life are the lineal descendants of those which 

 lived long before the Cambrian epoch, we may feel certain that the 

 ordinai'y succession by generation has never been broken, and that no 

 cataclysm has desolated the whole world." (Darwin — Origin of Species, 

 6th ed., 1875, p. 428.) 



" Upon any theory of ' evolution,' at any rate, it is certain that there can 

 be no total break in the great series of the stratified deposits, but that there 

 must have been a complete continuity of life, and a more or leis complete 

 continuity of deposition from the Laurentian period to the present day. 

 There was, and could have been, no such continuity in any one given area, 

 but the chain could never have been snapped at one point and taken up at 

 a wholly different one. The links must have been forged in different places, 

 but the chain, nevertheless, remained unbroken." (Dr. H. A. Nicholson — 

 Manual of PaloBontoloqy^ 2nd ed., 1879, pp. 49-60.) 



