518 PROF. J. W. SPENCER ON THE GEOLOGICAL AND [JSToV. I9OI, 



the Petit-Boiirg Series, etc. These drowned watercourses have a 

 depth of 40 to 60 feet, but near the margin of the sunken 

 terrace are gullies or canons, reaching a depth of 100 to 150 

 feet, where the neighbouring shoals are not covered by more 

 than 1 to 6 feet of v^ater, showing that the elevation reached this 

 amount, while there was a considerable removal of surface-loams. 

 Yet the epoch was not one of long duration, and in no way com- 

 parable in denudation to the epoch preceding it. 



Another subsidence of the land brought it down to about the 

 present level, although the reefs on the eastern coast are raised to a 

 height of 6 or 8 feet, suggesting a subsidence to that amount below 

 the present surface, and subsequent re-elevation ; but the small 

 oscillations of late date may be more or less local. 



The erosion-features of the mountain-mass are largely recent, 

 without the mass being deeply dissected by the torrential streams. 

 But the present volcanic activity dates back to the Lower Petit- 

 Bourg stage — close of the Pliocene (?) Period — prior to which the 

 mountains may have been no higher than those of Antigua. 



XII. Marie Galante, D^sirade, Petite Terre, anb The Saints. 



Long ago William Maclure reported the first three of these to be 

 limestone-islands, and we may infer from their position that their 

 history is doubtless that of Grande Terre. Desirade has a height 

 reaching to 912 feet, and Marie Galante attains an elevation of 

 672 feet, while Petite Terre is scarcely more than a low bank. 

 The Saints are old volcanic foi^mations with the highest points 

 reaching 1035 and 932 feet. All these outliers are much dissected 

 by the atmospheric forces, still very active, owing to the great 

 declivities of the land. 



XIII. Summary and CoNCL"crsio:Ns as to Changes of 

 Level of Land and Sea. 



(1) A land-surface throughout the Miocene-Pliocene Period, with 

 an elevation during the earlier days amounting to 2000 feet or more 

 above the present height (except the later volcanic mountain- 

 ranges), during the formation of the broad depressions between the 

 islands ; followed by a sinking of the land to somewhat near the 

 present altitude, and the formation of the undulating surface of 

 Grande Terre. 



(2) A submergence to 200 feet at about the close of the Pliocene 

 Period, with the accumulation of the Lafonde and Lower Petit- 

 Bourg gravels and loams and the Usine Limestones (?). 



(3) A re-elevation to about 3000 feet, shown within the region 

 of the archipelago — but this is only a small portion of the extreme 

 height indicated outside of the group— in the early Pleistocene 

 Period, with the formation of deep valleys and amphitheatres 

 dissecting the old rounded topography. It was during this time 



