MARINE. 259 



be difficult to distinguish between estuarine silts and silts 

 that are truly marine, but in all bays and recesses where 

 there is no great entering river, the formations may be 

 regarded as belonging exclusively to the sea. Besides 

 these Littoral or shore-formed silts, there are submarine 

 shoals and banks accumulating far from land, and sedi- 

 ments collecting in the stiller depths of the ocean. Every 

 chart bears witness to the numbers of these shoals and 

 banks, and in certain areas every throw of the sounding- 

 lead brings up evidence of the vastness of these Pelagic or 

 deep-sea deposits. On wave-washed shoals the accumula- 

 tions are usually sand and shingle ; but along the deeper 

 sea-bed they consist of slimy muds the " oaze " or " ooze " 

 of the navigator.* And were such pelagic deposits up- 

 raised into dry land, they would rival the older formations 

 alike in their geographical extent and in the diversity of 

 their mineral composition and organic remains. 



Besides these truly marine sediments, there is another 

 set of accumulations of vast extent and peculiar interest, 

 which are partly marine and partly ^Eolian or wind-formed. 

 We allude to the sand-dunes, sand-drift, or links, which 

 border most of the bays in our own islands, and indeed the 

 bays and sea-shallows of every other country. Originally 

 formed in the sea, the sands dried during neap-tides are 



* Speaking of this mud, Captain Dayman, in his ' Deep-Sea Sound- 

 ings/ says: "Between the 15th and 45th degree of west longitude lies 

 the deepest part of the ocean between Ireland and Newfoundland, vary- 

 ing from about 1500 to 2000 fathoms, the bottom of which is almost 

 wholly composed of the same kind of soft mealy substance, which, for 

 want of a better name, I have called oaze. This substance is remarkably 

 sticky, having been found to adhere to the sounding-rod and line through 

 its passage from the bottom to the surface, in some instances from a 

 depth of more than 2000 fathoms." On microscopic examination this 

 oaze was found to consist for the most part of foraminiferal organisms, 

 there being about 90 per cent of calcareous, and only 10 per cent of 

 siliceous matter ; the mass when dried greatly resembling chalk in colour 

 and consistency. 



