1913.] NATURAL SCIENCES OF PHILADELPHIA. 611 



washing from the hills carries land shells into the pond, and these 

 are mingled with the salt-water and brackish-water forms. But in 

 many cases, the swamp water becomes so foul during the change 

 from salt to fresh that no brackish-water forms can live in it. Appar- 

 ently, too, the change is rapid in some cases and no brackish-water 

 forms migrate in. The shallow ponds become swamps and finally, 

 draining to the sea, dry up completely and form level stretches 

 which are occupied by the "bush," and eventually by cultivations 

 of some kind. One such level stretch, formerly occupied, no doubt, 

 by one of these salt pond swamps, is now under cultivation as a 

 cocoanut plantation, near St. Mary's in the Valley. 



Along the east coast such salt ponds were not visited, and perhaps 

 they may no longer exist, but they are indicated on Nugent's map 

 as occurring at several places along the northeast coast of the island. 

 I have no doubt that the "horizontal marl" deposits in the vicinity 

 of St. George's Church have had some such history; and if the general 

 movement of the island is an upward one at present, as seems to be 

 the case, other shallow bays such as are found along this east coast 

 may develop into such salt ponds in the future. But the upward 

 movement would seem to be more characteristic of the west coast 

 than of the windward region, and the salt ponds of the west side of 

 the island are now forming and show all stages of development. 

 That such deposits must have occurred during the last emergence 

 of the island and that traces of them are still to be seen in the interior 

 (in the Central Plain, for instance) there can be little doubt. When 

 they are very shallow and dry up when in the salt stage, leaving 

 deposits of salt impregnating the surface soils, is probably indicated 

 in the large amount of salt found in the shallow surface wells in some 

 places at the present time. This salt impregnation of the soil in 

 certain parts of the Central Plain has been noted under the "shell 

 beds of the Central Plain." A local development of the same 

 ■character, due to the accumulation of salt in hollows, subsequent to 

 the last emergence of the island from the sea may be the cause of 

 the "gall spots" noted in the cane cultivations in the Central Plain 

 and eastward. These are places where the growth of the cane is 

 poor, and they are generally marked by a yellowness of the cane 

 itself. Mr. Tempany, Superintendent of Agriculture for the Leeward 

 Islands, who has made many soil and water analyses, agrees with me 

 that the gall spots are apparently places where soluble salts in the 

 soil have accumulated to a point which interferes with the growth 

 of the plants. 



