(34 REV. K. BARON— GEOLOGICAL NOTES [Feb. 1 89 5, 



"ninhase (279") A f ew m i les north °f the town of 



■^ V ' ' Vohimarina, lat. 13° 20' S. 



Hypersthene-dolerite ? (363) Village of Mandrisy, opposite the 

 (or norite ?) island of Ste. Marie. 



Epidote-rock (425) Long. 50° 10' E., lat. 15° 5' S. 



Emdote-schist (356) Near Soamianma, opposite the island 



F of Ste. Marie. 



Volcanic tuff (446) About lat. 13° 50' S. 



It may not be unworthy of note that pieces of pumice from 

 Krakatao lie strewn along the entire length of the east coast. 



Before concluding the remarks relative to the northern half of the 

 east coast, it may be mentioned that, although the rivers are 

 numerous, none of them can be spoken of as large. Close to the 

 sea however, most of them assume a considerable width, but this is 

 owi'ng to the heaping-up of sandbanks by the ocean waves. A few 

 miles inland they are mere streams. Some of them form lagoons 

 several miles in length, and what is sometimes given as the northern- 

 most limit of the numerous lagoons of the east coast is not actually 

 correct although those north of Tamatave are by no means so 

 numerous or so large as those south of it. 



IV. The Northern End of the Island. 



The part of the island here referred to is that which lies north of 

 lat. 13° S. In the neighbourhood of Andravina (lat. 12° 28' S.), on 

 the' eastern sea-board, and some miles south, there are numerous 

 patches of thick loose sand extending 3 or 4 miles inland. These 

 are apparently marine deposits. The River Lokia, a few miles north 

 of lat. 13° S., marks as nearly as possible the boundary-line between 

 the crystalline and the sedimentary rocks in the northern part of 

 the island for while immediately south of the river there are 

 here and there a few outcrops of sandstone lying on the crystalline 

 rock (o-ranitite), north of the river the central mountain-mass 

 (whichTis merely the end of the great mountain-chain forming the 

 backbone of the island) is composed of sedimentary strata, sandstone 

 appearing first, succeeded a little farther north and overlain by 

 oolitic limestone (467, 511, 519). This mountain-mass is not 

 improbably 1200 or 1400 feet high. On the east side of the island 

 it approaches the sea, being very steep, and leaving for the most 

 part a flat belt of low-lying land at its eastern base of only a mile 

 or two in width, and averaging perhaps 100 or 200 feet above the 

 sea. On its western edge it is much more broken up and some- 

 what lower in altitude, and is composed of fossiliferous sandstone 

 and oolitic limestone (480, 516). A comparatively flat area of 

 varying width, but probably averaging about 20 miles, extends from 

 its western base to the sea. Its extreme northern limit, where it 

 forms a steep bold front running for some 15 or 20 miles in an 

 easterly and westerly direction, and where it is composed mostly, if 

 not entirely, of oolitic limestone, occurs at lat. 12° 45' S. The dip of 



