THE ECONOMIC MOLLUSCA OF ACADIA. 53 



IReports, 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 

 first 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 Cajie 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 

 hardy 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 tne 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 

 jper annum on all its tidal margin."' 



