CHAPTER XL. 



CONSERVATION OF DEEP SEA BEDS. 



TEMPERATURE THE GULF STREAM THE EFFECTS OF TEMPERA- 

 TURE DEPTH AND DENSITY TIDES AND CURRENTS NATURE 

 OF THE SEA-BOTTOM DREDGING HARROWING AND TRAW- 

 LINGRINGS FOR MEASUREMENT REMOVAL OF CULCH FROM 

 PUBLIC GROUNDS. 



A. NATURAL CAUSES. 



IN the early chapters of this work I have already treated of 

 some of the conditions which affect the'growth, condition, 

 and production of oysters ; but there are certain active 

 causes influencing the formation of deep-sea beds which, 

 under the above head, form a necessary introduction to 

 Artificial Oyster Culture, of which it is indeed a part sub- 

 ject, and to which I will now refer. 



TEMPERATURE. 



Temperature acts in the greatest degree at the time of 

 spatting ; its after-influence gradually lessens as the oyster 

 grows and becomes more robust. In an early, warm sum- 

 mer, deep-sea oysters have been known to get "white- 

 sick" about the end of May, and " black-sick " a fortnight 

 or so later. If the season is late, thev may not become 

 white- sick until August or September, (a) 



(a) Anson & Willett's " Oyster Culture." 



