12-1 Annual Report of (he Natural History Society 



elding us bv the experience of continued observation, to indicate the 

 approach of those appalling hurricanes which often lay waste our Island. 



MINERALOGY. 



Dr. R. Lyall. known to the world by his publications relating to his 

 vojages, in which he has displayed varied and extensive information in 

 the sciences, has frequently favoured the Association with discussions on 

 Mineralogy. His residence in Madagascar, though distressing to his 

 family, was not a loss to science. The minerals which the inhabitants 

 wished him to convert into gold, and the serpents which the Queen of 

 the Ovaa caused to be introduced into his prison,* have been presented 

 to the Society. A Pluviometer, which oar colleague had placed upon 

 his house at Tananarho, made him be regarded as a magician. The 

 Rev. J. J . Freeman having exhibited to us various minexalogic speci- 

 mens which lie had brought fuom that country, Dr. Lyall made them the 

 subject of a report which wc possess. 



GEOLOGY. 



This scieuce, which, in the age of ljuflbn rested on so uncertain a 

 basis, has become in our days a scieuce of facts founded on observation. 

 It is now generally known by the title of Gcognosie ; especially where, 

 as in i. ur case, its investigations are limited lo a small portion of the 

 globe. 



Mr. J. Dcsjardius has described a cavern situate in the disA'ict of La 

 Rhriere du Rempart. It is with no great propriety that this crevice or 

 dcfich-iiey* in an inferior stratum, has been named « cmwrn. It however 

 possesses all the characters which distinguish the caverns of volcanic re- 

 gions. It has two oulluts, and its bottom is occupied by ,i poo] of 

 clear running Water. Its whole length is 240 foet, which, is but little 

 in comparison of that of La Rosieve or Daudin, in the district of Les 

 I'laines M'illicms, which was meusured by Messrs. Desjardins and G. 

 Houton, who penetrated to the extent of 2,t40 Trench feet. 



The Isle of Ambre has been the subject of a memoir by Mr. J. Desjar- 

 dins, explanatory of its Geognostic structure, and of its chief produc- 

 tions, both animal and vegetable. The assertion of Le Gentil, that it is 

 of Madrepore, is disproved. It has, like the Island of Mauritius, a vul- 

 canic basis; in various places, however, as is also the case in Mauritius, 

 there i3 met the detritus of molusca and polypes forming a conglomerate 

 • ontaining sometimes also fragments of basalt. 



Mr. U. Houton, struck with the singular structure of the Grand Basin, 



d its situation in the midst of forests, at the altitude of 260 fathoms 

 above the level of the sea, read to us a memoir, in which he concludes, 

 that this mass of water rests in tho crater of an extinct volcano. It i 3 

 well known that craters have been extinguished in various quarters of 

 the globe, and that a lake has taken the place of a liery aperture. 



Mr. tioart, who resided for some time iu the Isle liodriguc, and who 

 in his occupation of Geographic Engineer, has visited every part of it, 

 communicated to the Society a memoir on its Geognostic structure ; and 

 has presented ua with a topographic plan of it, and a sketch of a grotto 

 (bund there, which nbounds with stalagmites and stalactites of singular 

 forms nnd dazzling whiteness. 



• It was explained at the Meeting of the Institution, when this report was 

 rend, that the employment of these serpents was not a measure of cruelty on 

 the part of the Oras, hut an) artilice of the priests, who thereby wished to 

 represent their divinities as incensed at his abode in their country. Dr. Lyall 

 then inhabited a native hul in a village, under ionic slight restriction, — 

 I'../. Quarterly Journal- 



