?,?'? 8URYEY OF THE INTERTROPICAL ism. difficult, and even dangerous, for the stones were o?.z, so loose and decomposed, that no solid footing could be found. The top of the rock is covered with a thick brush of acac/? leucoph?a, (of La- crosse Island,) many trees of which were obliged to be cut down or cleared away before the various objects could be seen from the theodolite. Mr. Cunningham collected here specimens of eighteen different sorts of plants. Bat Island is a mass of sandstone superincum- bent upon a quartrose basis, and intersected by nearly vertical veins of white quartz, the sur- face of which was.in a crystallized state. The floor of the cavern was covered with heaps of water-worn fragmems of quartzose rock, con- taining copper pyrites, in some of which the cavities were covered by a deposit of greenish calcedony. The sides of the earera had a sta- lagmitical appearance, but the recess was so dark, that we could not ascertain either its forma- tion or extent; it did not, however, appear to be more than twelve or fourteen yards deep. On first entering it we were nearly overpowered by a strong sulphureous smell, which was soon ac- counted for by the flight of an incredible number of sinoil b?ts, which were roosting in the bottom of the cave, and had been disturbed by our ap- proach. We attempted to grope our way to the
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