NOTES ON MARINE DEPOSITS OF THE FIRTH OF FORTH. 247 



4. The amount of detrital and other matter brought to and 



deposited over these areas from rivers, general land 

 drainage, and disintegration of the coast line. 



5. The amount of material deposited from steam-ships, 



dredgers, and sewage, or solid matter in suspension. 



Or one might put the question in two words — are the 

 deposits clean or 'polluted ? Upon the greater or less degree the 

 grounds are affected by these agencies, will the destruction of 

 the bottom-living and pelagic animals and movements of the fish 

 be regulated. 



The Firth of Forth may, perhaps, be taken as a more or less 

 typical example. Not many years past in this area marketable 

 fish were to be taken in plenty, while we know at the present 

 time comparatively few can be captured either by trawl, line, or 

 other appliances. Continuous trawling would, doubtless, in such 

 a restricted area, soon clear it of fish for a time, but if left 

 undisturbed for a reasonable time, there can be little doubt that 

 it would become repopulated were the surrounding conditions 

 favourable, which is the case where ordinary natural conditions 

 of the sea are not disturbed or polluted. It will not be disputed 

 that where the water is pure and the deposits not continually 

 disturbed or polluted, everywhere at a reasonable depth, from 

 the tidal line downwards over the sea floor, marine life is 

 abundant, and that the lower animals furnish the chief food of 

 the higher forms. 



The examination of the deposits found in the area under 

 consideration, and described in these notes, indicate fully that the 

 conditions are not favourable to the attraction and necessary 

 support of marine life, especially of any large quantity of fish 

 whose chief food consists of invertebrate animals which live in 

 and on the deposits over its floor. Not many years past there 

 was to be found living, generally distributed over the floor of the 

 Firth of ForthJ patches or banks of considerable extent, covered 

 thickly with living Pecten opercularis, L. ("clam" of the fishermen); 

 Turritella terebra, L. (a long, conical, univalve Mollusc) ; Ostrea 

 edulis, L. (oyster) ; Mytilus edulis, L. (the common mussel) ; 

 JBuccinum undatum, L. (buckie) ; and other Mollusca, with 

 abundance of many species of invertebrate animals, as Crustacea, 

 Annelids, Echinoderms, Hydrozoa, &c, &c, "fish food." At 



