18 • TRANSACTIONS OF THE [OCT. 13, 



Evidence of Subsidence and Elevation. 



The facts bearing on the question of subsidence and elevation 

 have already been given, but it may be worth while to briefly 

 review them and give my inferences. 



The caves and old beaches now above the sea plainly show 

 where the level of the water formerly was. The section at 

 Fresh Creek proves, as do the other cases of elevated corals, that 

 the island has been elevated. As the formation on top of the 

 corals at Fresii Creek is ^olian, it follows that it could have 

 been deposited only above water; and as the caves and old beaches 

 are at least thirty feet above the sea-level and in the ^olian 

 formation, they could not have been formed until the islands had 

 subsided. Hence we are justified in assuming that at some pre- 

 vious time in their history the islands were at about the same 

 level as now. Then followed a period of subsidence of at least 

 thirty feet, during which the caves and old shoi*e lines were 

 formed. After this subsidence the islands were elevated to 

 about their present position. It only remains to sum up the 

 facts that bear on the question of the most recent movement in 

 the Bahamas. 



The fact that on the west coast of Andros, where the slope 

 seaward is so exceedingly slight, the soft, calcareous mud grows 

 gradually harder and harder as we go inland, indicates to my 

 mind that the island has been recently rising; for if it were sub- 

 siding or had recently subsided, we may suppose that time 

 enough would have elapsed since its elevation to allow the calca- 

 reous deposit to harden into rock, and then, as the subsidence 

 took place, the surface at the edge of the water would be hard 

 rock, which would finally probably extend under the water as 

 the latter encroached on the land. The depth, close to the 

 shore, of the fine calcareous deposit also points to elevation, for 

 in it I ran a pole nine feet. How much deeper it was I had no 

 means of determining, owing to the length of the pole. Now, 

 had subsidence been taking place, should we find this depth of 

 calcareous mud close to the shore ? It is perhaps possible, and 

 it might be claimed that the greater the subsidence the greater 

 would be the depth of the mud ; but by the time that nine feet 

 of sediment had been laid down it is reasonable to suppose that 

 the mud on the shore would have hardened, and then should we 

 not find the water washing against a rocky shore ? 



As we approach tlie west side of Andros from the interior the 

 pines grow smaller and smaller, and the forest is often prolonged 

 into points that run out in the swash and are composed of 

 young and vigorous trees. There are also in the swash small 



