Vol. 51.] OP A JOURNEY IN MADAGASCAR. 71 



on the sea-shore near Belfast in the north of Ireland. Here it may 

 be mentioned also that an interesting rock allied to Rosenbusch's 

 camptonite, together with an andesite, occurs east of the village of 

 Jangoa (long. 48° 19' E., lat. 13° 40' 8.). 



We see, therefore, that in this north-western part of Madagascar 

 both intermediate and basic lavas occur, consisting of trachyte, 

 phonolite, haiiyne-nepheline-phonolite, andesite (rare), basalt, and 

 oli vine-basalt. 



At Ambavatoby, a small bay on the mainland south-west of the 

 island of Nosibe, coal of excellent quality is said to have been 

 obtained (see ' Annales des Mines,' 1854, 1856, 1866). I visited 

 all the points in this bay where coal is said to exist, and could find 

 nothing but thin seams of carbonaceous shale intercalated among 

 (Jurassic ?) sandstones. What there may be below the surface I 

 cannot of course say, but am strongly inclined to doubt altogether 

 the existence of coal. This carbonaceous shale, it may be men- 

 tioned, occurs at several points on the roundish headland south of 

 Nosibe. 



Such is a brief account of some of the more salient features in 

 the geology of those parts of Madagascar traversed during my 

 journey, and I trust that, in spite of its imperfection, this account 

 will not be found altogether devoid of interest from the geological 

 point of view. 



Perhaps I may be allowed here to make one or two slight altera- 

 tions and corrections of my former paper entitled ' Notes on the 

 Geology of Madagascar,' Quart. Journ. Geol. Soc. vol. xlv. (1889). 



P. 308, — In first paragraph under ' Crystalline Schists, etc' 

 instead of ' Por instance .... 60 or 80 miles,' read : ' Por instance, 

 a large area in the interior, reaching from about the capital 

 to at least 100 miles north of it, and probably 60 or 80 miles 

 in width, consists of gneiss with the strike of the foliation 

 running generally in a north-westerly or north-north-westerly and 

 south-east or south-south-easterly direction, or approximately 

 thereto.' 



P. 311, lines 9 and 10 from top. — For ' It is a reddish rock. . . . 

 decayed gneiss,' substitute : ' This rock may be described as 

 sillimanite-schist, being composed of sillimanite and quartz, with 

 abundant almandine-garnet, by the presence of which the rock is 

 coloured red.' 



On map. — For ' bosses of diorite ? ' read ' cones of nepheline- 

 phonolite.' 



EXPLANATION OF PLATE I. 



Geological Sketch-map of the extreme north end of Madagascar. 

 Scale : 1 inch = 30 miles. 



[For the Discussion on this paper, see p. 92.] 



