250 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



the Firth, and purity of its waters, at dilTerent seasons of the 

 year, by the greater or less amount of detrital and solid matter 

 in suspension. 



These pelagic ox-ganisms are usually, under ordinary circum- 

 stances, in such quantities that vast numbers of them are 

 constantly dying off with the ever-changing physical and 

 developmental conditions in the surface and sub-surface waters ; 

 their remains, sinking to the bottom, carry down with them 

 quantities of organic material, forming one of the chief factors 

 from which many of the bottom-living animals derive their 

 food supply. The want of this constant supply in the Firth of 

 Forth would be disastrous to their existence. 



That a great destruction of many of the more important 

 forms of marine life on the floor of the Firth of Forth has taken 

 place there can be no doubt. In the case of the Oyster, Clam, and 

 Mussel it has been well known for some time. To account for 

 this serious destruction many causes have been put forward from 

 time to time. The most likely may be mentioned here : — (1) 

 reckless Ashing; (2) deposition of peat, &c., brought down the 

 Forth from its upper reaches by currents ; (3) deposition of mud, 

 tic, from harbour dredgers ; (-i) pollution from oil and other 

 factories situated along its shores ; (5) changes in the seasons ; 

 (6) the throwing over of ashes and "clinker" from steamers. 

 With the exception of the first, perhaps, all the causes above 

 mentioned are strikingly illustrated by the examination of the 

 deposits found all over the area between Inchkeith and May 

 Island. Not one of the samples examined by me can be said to 

 be free from one or other of these polluting substances. 



It is also true that during the winter months and early 

 spring the waters of the Forth often become heavily laden 

 with fine argillaceous matter in suspension. A large amount of 

 dredged matei'ial from harbours have been and are still deposited 

 in this area. The number of steam-ships entering and leaving 

 the Firth have greatly increased, and are answerable for many 

 thousands of tons of material in the form of ashes, " clinker," &ic., 

 indiscriminately thrown overboard and distributed over its floor. 

 An increase of sewage and other detrital matter constantly enters 

 its waters. This, with any sudden extra large amount of argil- 

 laceous matter brought down by the rivers and general land 



