THE USES OF SEA-WEEDS. 71 



quarry near Ardrossan I saw numerous dark impressions 

 of a large Sea-weed, resembling Haliclrys. Nay, we have 

 practical proof that the disjecta memhra of Sea- weeds, buried 

 in the mud, are well fitted to contribute to its consolidation. 

 Mrs. Marshall, a talented and scientific lady of my acquaint- 

 ance, after attending a meeting of the British Association, 

 was led to ponder on the formation of rocks, and being a 

 chemist, she thought she would try to construct them arti- 

 ficially. Many rocks, she observed, had been formed by 

 stratification, — some at the bottom of fresh-water lakes, — 

 others in estuaries, or at the bottom of the sea. What 

 then must have been the component parts of the latter — of 

 limestone, for instance? They are full of the organic 

 remains of MoUusca and Zoophytes, whose habitations were 

 formed of carbonate of lime, which they had the power of 

 extracting from the sea. These shelly abodes of Mollusks, 

 wdth the polypidoms of Zoophytes, such as corals, would often 

 be broken in pieces and ground into powder by the mighty 

 turmoil of the sea, and subsiding from time to time, would 

 form strata of calcareous mud in which shell-fish and other 

 marine animals would be buried. Alons- with these, there 

 would constantly be mixed immense masses of Sea-weeds 

 torn by storms and currents from the submerged rocks. 



