PHYSICAL CHANGES 223 



remains of leaves and branches, together with bones, not to 

 mention other evidence, there is no doubt that much of what 

 is now open down and bare hill was formerly covered with 

 forest. There was therefore appropriate habitat for them all ; 

 and their needs, whether in water or on the trees, would be 

 met by the former conditions of the country. It seems highly 

 probable that the physical changes of the interior have been the 

 chief cause of the extinction of so many living creatures, al- 

 though the advent fcf man upon the scene may have hastened 

 the process. 1 



As this chapter necessarily touches less on popular and more 

 on scientific matters than the rest of this book, a few more 

 words may be added on the palaeontology and geology of 

 Madagascar. Besides those extinct creatures already spoken 

 of, remains of gigantic tortoises have been discovered ; also 

 species of swine and river-hog ; an ox differing from the existing 

 cattle of the country, and a large rail and a goose exceeding in 

 size any living species. All these belonged to the Quaternary 

 and Recent geological epochs. But far back in the period 

 of the Secondary rocks a species of sloth lived in the forests, 

 old forms of crocodile lived in the rivers ; and there were three 

 at least of those gigantic lizards which were the largest of all 

 known land animals, and were the master existences of the 

 Jurassic period. 



To sum up in a sentence or two the salient features of Mada- 

 gascar geology, it may be said that the whpjle easternj)art of the 

 island from north to south, comprising probably about three- 

 fifths of the entire area, is composed of crystalline rocks gneiss, 

 granite, mica-schist, etc. But the western two-fifths of its 

 surface consists chiefly of Secondary strata, including chalk 

 and sandstones and limestones of the Jurassic and Cretaceous, 

 periods, as well as a smaller area of rocks of the Eocene and 

 Oligocene eras. A fringe of Quaternary deposits is also found 

 along a great part of the west coast. It is evident, therefore, 

 that the western side of the island has been repeatedly under 

 the sea during the geological periods just mentioned, leaving the 

 upper highland of ancient rocks as an island not half the extent 

 of the present Madagascar. It has quite recently been found 

 that a narrow edging of chalk rock extends for about one hun- 

 dred and twenty miles on the central part of the east coast. 2 



