Vice-President's Address. 201 



climatic conditions of l\ilceozuic, Mesozoic, and Cainozoic 

 times. On the contrary, it seems to me to gain additional 

 support from the very evidence to which Nordenskiold and 

 others have appealed. 



Note. — The accompanying maps (Plates VIII. and IX.) require a few 

 words of explanation. The geology of the world (Plate IX.) is still so imper- 

 fectly known, that any attempt at graphic representation of former geographi- 

 cal conditions cannot but be unsatisfactory. The approximate positions of 

 the chief areas of predominant elevation and depression during stated periods 

 of the past may have been ascertained in a general way ; but when we try to 

 indicate these upon a map, such provisional reconstructions are apt to suggest 

 a more precise and definite knowledge than is at present attainable. For it 

 must be confessed that there is hardly a line upon the small maps (A, B, C, 

 Plate VIII.) whicli might not have been drawn differently. This, of course, 

 is more especially true of South America, Africa, and Asia, of large areas of 

 which the geological structure is unknown. But although the boundaries of 

 the land-masses shown upon the maps referred to are thus confessedly pro- 

 visional, the maps nevertheless bring out the main fact of a gradual growth 

 and consolidation of the land-areas — a passage from insular to continental 

 conditions. I need hardly say this is no novel idea. It was clearly set forth 

 by Professor Dana upwards of forty years ago {Sillimans Journal, 1846, 

 p. 352 ; 1847, pp. 176, 381) ; and it received some years later further illustra- 

 tion from Professor Guyot, who insisted upon the insular character of the 

 climate during Palaiozoic times {The Earth and Man, 1850). It must be 

 understood that the maps (A, B, C, Plate VIII.) are not meant to exhibit the 

 geographical conditions of the world at any one point of time. In IMap A, 

 for example, the area coloured blue was not necessarily covered by sea at any 

 particular stage in the Palaeozoic era ; it simply represents approximately the 

 region over which Palaeozoic marine strata are believed to extend or to have 

 extended. But, as already stated, numerous oscillations of level occurred in 

 Palaeozoic times, so that many changes in the distribution of land and water 

 must have taken place clown to the close of the Permian period. The land- 

 areas shown upon the map are simply those which a})pear to have been more 

 or less persistent through all the geographical changes referred to. Similar 

 remarks apply to the other maps representing the more or less persistent 

 land-areas of Mesozoic and Tertiary times. Thus, for example, there are 

 reasons for believing that Madagascar was joined to the mainland of Africa at 

 some stage of the Mesozoic era, but was subsequently insulated before Tertiary 

 times. Again, as Mr Wallace has shown, there is every probability that at 

 some late stage of the Mesozoic era a land-connection obtained between New 

 Zealand and Australia. The same naturalist also points out that a chain of 

 islands, now represented by numerous islets and shoals, served in Tertiary 

 times to link Madagascar to India. Map D shows the areas of predominant 

 elevation and depression. The area coloured brown represents the great 

 continental plateau, which extends downwards to 1000 fathoms or so below 

 the present sea-level. The area tinted blue is the oceanic depression. From 

 the present distribution of plants and animals we infer that considerable 



