166 APPENDIX TO REPORT ON OYSTER CULTURE 



APPENDIX H. 



Report on the Composition of the Soils of Oyster Grounds ; 

 and on the Qualities which exert most Influence on Oyster 

 Cultivation, by W. K. Sullivan, Ph.D., Professor of Che- 

 mistry to the Catholic University and the Royal College of 

 Science, and Secretary of the Royal Irish Academy. 



The circumstances which influence the production and growth of the 

 animals which inhabit the sea-shore are : — 



1 . Temperature ; 



2. Depth of water at high and low water ; 



3. Comparative amount of sunshine, especially the relative amount 



which falls during low water in the spawning season ; 



4. Saltness of the water, in connexion with great rainfalls, and the 



influx of fresh water from rivers and brooks ; 



5. Currents; 



6. Suspended matter ; 



7. Nature of the shore and sea bottom. 



Temperature may be considered from three points of view : — the mean 

 annual temperature of the water, the maxima and minima temperatures 

 during the season of spawning, and the mixture of currents of cold and 

 warm waters which is very destructive to some kinds of animals, espe- 

 cially if it occurs during spawning. 



The depth of water influences the amount of light which penetrates 

 the water, the aeration of the water, and the temperature. 



The amount of sunshine influences the amount of oxygen in the water, 

 and consequently the greater or lesser activity of all forms of animal 

 life. When high water occurs about noon, during the time of reproduction 

 of the animals and plants which live in the intertidal zone, the action of 

 the ^un is greatest, and the development of life most active. It is the 

 reverse in the zone beyond low water-mark. The young of those animals 

 which spawn in shallow water, beyond low water-mark, when the tide is 

 low, and when low water occurs in the middle of the day in summer, 

 develop more rapidly than when the spawning takes place in very deep 

 water, and when low water occurs in the evening or morning. The 

 height to which the tide rises is otherwise also of importance, not only to 

 the zone between low and high water, but to the zone beyond low water- 

 mark. The alternation of deep and shallow water exposes the plants and 

 sedentary animals to successive alternations of temperature, and to great 

 variations in the amount of gases in the water. 



Great falls of rain sometimes suddenly add such quantities of fresh 

 water to the inner zone of sea water as to materially alter, often for 

 many hours, the character of the water. Such a change must seriously 

 affect young animals if it takes place during spawning. The same effect 

 is permanently produced in estuaries and bays into which rivers flow. 

 In this case the marine fauna differs from that along the shores of the 

 open sea. Even here the production of certain forms of animal life may 

 be greatly affected by a sudden accession of fresh water brought into 

 the estuary by floods. Fresh water also brings down large quantities of 

 organic matter in solution and in suspension ; the drainage of cities and 

 towns, which helps the development of certain kinds of infusoria?, favours 

 the growth of certain plants and animals, and retards that of others. 



Strong currents and waves exert very great influence on animal life, 

 especially on its distribution. Animals and plants do not thrive, as a 

 rule, where the water is agitated very much ; indeed shingle shores, 

 over which the waves break with violence, are notoriously barren of life, 



