THE ECONOMIC MOLLUSCA OF ACADIA. 
53 
►Reports, we have had constant information in the Reports of 
Mr. Venning, of New Brunswick, and Mr. J. H. Duvar, of 
Prince Edward Island, as to the condition of the beds. Mr. 
J. F. Whiteaves, of the Dominion Geological Survey, has 
given them some attention; his reports are mentioned below. 
In the Tenth Census of the United States, Section X., Mono, 
.graph B, Report on the Oyster Industry of the U. S., pp. 3-11, 
Mr. Ernest Ingersoll has given a concise account of the his- 
tory and present condition of the beds and a not very encour- 
aging sketch of their probable future. Other than these we 
have found no writers who have discussed the Canadian Oyster- 
beds. 
If we pass, now, from human to geological history, the 
rfirst question which meets us is, how the Oysters came first to 
be in the Gulf, far removed as they are from their congeners 
to the south of Cape Cod? This problem has already been 
briefly discussed in the introductory part of this paper (p. 17.) 
But the causes which brought about the present condition of 
affairs are still at work, and are producing slow but constant 
•changes in the beds. A depression of the land is certainly 
going on in this region and must cause changes in tides and 
•currents, and a more active erosion* of the land and disposi- 
tion of silt. To this, rather than to the action of ice, as some 
have thought, is probably to be referred the greater part of 
the destruction of former large Oyster-beds, the sites of which 
are marked all around Prince Edward Island especially, by 
immense deposits of dead shells. Oysters, though they flourish 
on mud bottoms, quickly perish if mud covers them. 
There are other purely zoological causes also at work. 
The depression of the land must allow the cold waters of the 
deeper part of the Gulf to come nearer and nearer to the 
shore, making the conditions more and more favorable for the 
Rardy northern animals, and less so for the more sensitive 
southern forms. The young of the latter must have warm 
*Mr. J. H. Duvar, in a letter to the writer, says:— “ The Island itself is washing 
. away at an appreciable rate,— the late Mr. Anderson, Government Surveyor, . . . 
told me that he had observed and estimated the decrease of the land, at one foot 
per annum on all its tidal margin / 1 
