35 CORAL AND MINERALS. 



tuffs, and volcanic rappilis. This essay is accompanied by a 

 complete geological map of N6sibe\ 



Since the date of this last paper some further attention has 

 been paid to this part of the country, in connection with the 

 French company promoted by M. Lambert (see Annales des 

 Mines, 6me sene, t. x. pp. 277—319), but hardly anything 

 more has been done towards a scientific examination of other 

 portions of Madagascar, except a notice of the peninsula en- 

 closing Antongil Bay on the north-east coast (Bull, de la Soc. 

 de Oiog., Sept. et Oct. 1867), although probably M. Grandidier 

 will have some fuller information in his great work now in 

 progress. 



It may be here observed that a (barrier ?) reef of coral 

 extends from 200 to 300 miles along the south-east coast of 

 Madagascar, varying in its distance from the land from a 

 quarter of a mile to three or four miles ; while fringing reefs 

 surround the northern end of the island, extending for 250 

 miles along its western side, and for 400 miles down its 

 eastern side, and are also found on the south-west coast. Mr. 

 Darwin gives in his work on " The Structure and Distribu- 

 tion of Coral Beefs" (pp. 104, 105) some facts showing the 

 wonderfully rapid growth of various species of coral on the 

 east coast of Madagascar. The northern extremity of the 

 country is said by Captain Owen to be formed of madre- 

 poritic rock. 



With regard to minerals, Madagascar is tolerably rich in 

 some of the most useful metals. Iron is found in great 

 abundance in Imenna, sometimes almost in a pure state. In 

 some of the hills it is so plentiful that it is difficult to get a 

 bearing with a compass from the deflection caused by the iron 

 in the ground. Copper and silver have also been discovered, 

 and from the geological structure of the country it is highly 

 probable that gold would also be found in some of the ravines 

 of the granitic highlands ; but as it is at present a serious 

 offence against the native laws to search for the precious 

 metals, hardly anything has been done in this direction. 

 Eock-salt is found near the coast, and nitre is also met with. 

 Iron pyrites, from which sulphur is extracted, is also found 

 in abundance; and in the northern part of the island 



