AGASSIZ : BAHAMAS. 149 



from Grenada. It becomes materially wider north of Martinique. This 

 is indicated by the two small banks lying northeastward of Martinique 

 between it and Dominica. North of Dominica, Marie Galante, and Gua- 

 deloupe with its outliers of Desirade aud Petite Terre, occupy nearly the 

 whole width of the ridge to the 500 fathom line on either side. It again 

 increases in width at the line from Nevis to Barbuda, aud attains its 

 greatest lateral dimensions on the line from the western edge of Saba 

 Bank to the edge of the bank east of St. Martin, one fold of the ridge 

 extending from Saba Bank to Santa Cruz and another to Sombrero, the 

 valley between them falling off rapidly to the Anegada Passage. 



The northwest end of St. Vincent rises abruptly to three thousand feet. 

 On the east side of Calliaqua Bay there is a lagoon protected by a reef. 



The Pitons of St. Lucia are between three aud four thousand feet 

 high. At Laboise the shore is skirted by a reef. 



The depths of the passages between the banks of the Windward Isl- 

 ands are quite moderate. Only in the channels between Dominica and 

 Martinique and between Martinique and St. Lucia do we get a depth of 

 more than five hundred fathoms (in oue case 548 fathoms, in the other 

 575), the 500 fathom line joining St. Lucia and St. Vincent to the Grena- 

 dines Bank, and the 500 fathom line uniting Dominica with all the banks 

 to the south of Sombrero with the exception of Santa Cruz and the two 

 submarine banks between it and Sombrero. 



Dominica (Hydrographic Chart No. 1318), which rises to over forty- 

 seven hundred feet, is, like Martinique, flanked on the east by a plateau 

 of considerable width limited by the 100 fathom line. Between it and 

 Martinique to the eastward rises a small bank, with a depth of forty 

 fathoms. The northeast end rises less abruptly from the sea, the sound- 

 ings off the coast showing a continuation of this gradual slope, the 100 

 fathom line being three and a half miles off shore. It is interesting to 

 compare the submarine slopes of Dominica, Martinique, St. Lucia, and 

 St. Vincent with the steep slopes of the Bahama Banks, which have been 

 considered by many writers as due to the continuous growth of coral 

 reefs during subsidence, so as eventually to form walls of limestone 

 rising abruptly from nearly two thousand fathoms in depth. It is sur- 

 prising to find that it is the western faces of these islands which give us 

 the abrupt slopes, while the eastern faces, on which the coral reefs are 

 found growing upon a limestone bank of considerable width, show a 

 comparatively gentle slope. 



The 100 fathom line surrounding Guadeloupe does not include within 

 its limits the volcanic summits of the Saintes, or the elevated limestone 



