Vol. 51.] GEOLOGICAL NOTES OE A JOURNEY IK MADAGASCAR. 57 



7. Geological Notes of a Journey in Madagascar. By the 



Rev. Richard Baron, F.L.S., F.G.S. (Read November 21st, 



1894.) 



[Plate I.— Map.] 



Contents. Page 



I. Introduction 57 



II, The Country between the Capital and the East Coast 57 



III. The East Coast 60 



IV. The Northern End of the Island 64 



V. The North-west Coast and Islands 67 



Geological Map of Antsihanaka Province 58 



I. Introduction. 



In the course of the year ] 891 it fell to my lot to undertake a long and 

 interesting journey of about 1200 miles in the island of Madagascar, 

 during which I was able to make a few geological notes that may 

 not be unworthy of record. Leaving the capital, I proceeded in a 

 north-easterly direction as far as Imerimandroso, 1 in the province of 

 Antsihanaka; then struck due east, reaching the sea at Fenoarivo, 

 a town situate about lat, 17° 25' S. From here I followed the eastern 

 coast, mostly along the water's edge, as far as the Bay of Diego 

 Suarez, in the extreme north of the island ; and thence I travelled 

 down the north-western coast as far as the River Mevarano, in lat. 

 14° 37' S., finally proceeding by boat to the island of Nosibe (long. 

 48° 15' E., lat. 13° 20' S.), visiting several of the smaller islands on 

 the way. It is, of course, impossible to give a detailed account of the 

 geological features of the country traversed during such a journey; 

 but, as so little is known of the geology of Madagascar, a general 

 sketch may not be without value. I may say that specimens of all 

 the different rock-types met with on the route were collected, and I 

 hope to give a detailed description of them as soon as practicable. 



For the sake of convenience, the part of the island travelled over 

 may be divided into four sections : (1) that between the capital and 

 the east coast, (2) the east coast (that is, the northern half of it), 

 (3) the northern end of the island, and (4) the north-west coast and 

 islands. These I shall now briefly describe in order. 



II. The Country between the Capital and the East Coast. 



By far the most predominant rock between Antananarivo, the 

 capital, and the east coast is a hornblende-granitite-gneiss. This 

 rock, which covers so wide an area in the eastern half of Mada- 

 gascar, is, for the most part, of a greyish or bluish-grey colour and 

 of medium texture, and consists essentially of felspar (orthoclase and 

 plagioclase), quartz, dark mica, and hornblende. It not infrequently 

 becomes garnetiferous, but otherwise generally varies little in minera- 



1 Except when otherwise mentioned, the native names are those of towns and 

 villages. 



