954 



SCIENCE. 



[X. S. Vol. XXI. No. 547. 



cause of submergence from a time of a more 

 continuous land surface, partly because of 

 shore erosion, which goes on furiously during 

 autumnal hurricanes. The submergence is 

 inferred to have amounted to 300 feet, because 

 the islands are honeycombed with caverns, of 

 which the deeper ones descend 300 feet be- 

 neath present sea level.* Observations by the 

 geologists of the expedition indicate that the 

 submergence of the islands has recently been 

 somewhat greater than now, for stratified de- 

 posits containing fossils of living marine spe- 

 cies are found at altitudes of fifteen or twenty 

 feet at many places. Whether the islands are 

 now rising or sinking is not asserted, but the 

 bench marks that were set up and carefully 

 measured with respect to sea level will make 

 it possible to answer this question within a 

 few score years. 



The shallower parts of the submarine plat- 

 form are so thickly studded over with coral 

 reefs that it has proved impracticable to chart 

 them. At certain points the platform is 

 pierced with ' ocean holes,' or areas of deep 

 blue water in the midst of the shallower green 

 sea. Here the tide ebbs and flows through 

 sub-platform passages; in one instance that is 

 described a descending eddy was noted, with 

 concave surface and foaming center. The 

 tides were carefully observed at Xassau and 

 * This line of argument is in accord with cur- 

 rent geological opinion, yet it does not appear to 

 be altogether proved that submarine caverns may 

 not be dissolved out by fresh-water streams which 

 descend beneath the level of the sea and rise again 

 to the sea floor; just as caverns are conceivably 

 formed beneath the level of the ground-water 

 table on the land. Many land caverns now above 

 the water table are filling with calcareous de- 

 posits; the excavation of such caverns by solution 

 may have taken place before the neighboring 

 valleys were worn to their present depth, or when 

 the region stood at a lower level, so that the 

 cavern zone was beneath the water table, and the 

 growing cavern was fill^ with water. Whether 

 the cavern zone was beneath the land or beneath 

 the littoral sea floor is immaterial, so long as the 

 ground water is kept in motion. Is it not indeed 

 possible that the excavation of some submarine 

 caverns was begun as well as continued by the 

 tidal currents now flowing through them? 



thus better determined than ever before for 

 these islands; they are shown to be of the 

 Atlantic type, that is, with two subequal high 

 tides in each lunar day; and not of the Gulf 

 type, in which, as a rule, only one tide occurs 

 each day. The mean tidal range is 2.634 feet, 

 with spring and neap means of 3.051 and 

 2.129 feet; the mean lunitidal interval or cor- 

 rected establishment of the port is 7 h. 22.8 m. ; 

 but the variation of this interval due to pri- 

 ming and lagging may amount to 45 minutes. 

 The well-known uniformity of the Bahaman 

 climate is attested; even in early summer, 

 temperatures of 80° or 90° were not oppres- 

 sive, the air being moderately dry and usually 

 in motion. Flights of kites and observations 

 on clouds indicated a diminution in the 

 velocity of the prevailing easterly trade wind 

 above 4,000 feet altitude, a curious contrast 

 to the conditions obtaining in temperate lati- 

 tudes where an increase of velocity with 

 height is the rule. 



The soils of the islands are described in 

 greater variety than one might expect on a 

 foundation exclusively calcareous, seven types 

 being recognized. The most important are 

 the black loam and the red loam. The former 

 occupies about three fourths of the surface, 

 and makes what is known as ' provision land,' 

 because of its use for subsistence crops. It 

 is good for citrus fruits, among which the 

 shaddock or grape fruit takes the lead; but 

 this soil is so thin that when fruit trees are 

 planted, a hole is first blasted in the under- 

 lying rock. Sisal, which is destined to be an 

 important product, and cotton, more impor- 

 tant formerly than now, also grow in this soil ; 

 the cotton plant grows tree-like, living over 

 several seasons and having to be pruned to 

 keep its branches within reach. The red 

 loam soil is the best for pineapples, a very 

 important crop, as over seven million dozens 

 were exported in 1902, yielding almost $200,- 

 000; but the prices have fallen in recent years, 

 partly on account of the poor treatment of th? 

 pineapple in marketing it. The receipts from 

 this source are at present much exceeded by 

 those from sponges. 



We shall pass rapidly over the biological 

 chapters. There is an elaborate list of plants. 



