fi24 REV. THOMAS BROWN ON THE ARCTIC SHELL-CLAY 



fusedly cast together with other materials, I feel as if the evidence, had it stood 

 alone, would have been far from decisive. These two deposits, then, taken together, 

 form the first and most recent stage. 



II. — The Sands and Clays along the Banks of the Stream. 



This second stage is seen only in Section IV. Along the course of the 

 stream are the present banks, corresponding with the first stage. But farther 

 back, on either hand, and rising higher, is the deposit in question, which repre- 

 sents a previous state of things. A little above the foot-bridge the stream has 

 cut into it, and laid open the following section already referred to. In this the 





___- — ~—~^ZZ:.; . ■-- 







I ^fyp£S::£v : ;i ':: ■-:.::;:■■ ..:;■ -^l? ~\ 



Blown sand. 





?, »; _-- "-"''' ' r • ' • • ^^t^~-__: — __j__________ 







, ,_--_-- -—-=—Z~~====~ = ===^^^=z^^!=L 



Clay with Scrobicularia. 

 Sand and clay, shells 



Ilisrh-water mark. 



■^■l 



at bottom. 

 Blue clay. 



Fig. 6. 



bed No. 2 deserves particular attention, as furnishing good evidence of a rise in 

 the bed of the sea. It consists of a layer of fine clay, about a foot in thickness, 

 running all along the section, immediately under the blown sand, and contains a 

 good many shells of a single species, the Scrobicularia piperata. It may be 

 termed the Scrobicularia bed. Now, the remarkable thing is, that almost the 

 whole of these shells are in an erect position, with the siphonal end uppermost — 

 showing, as every conchologist knows, they are at home just in the position in 

 which they were when alive. The habits of the shell are well enough known. 

 It burrows in clay at the mouths of rivers, sending up its long siphons to draw a 

 continuous stream of water into its gills, so that in this bed the shells are in the 

 position in which they lived. The habitat of the shell also is peculiar and well 

 marked. It enters the mouths of tidal rivers, but never goes out of the reach of the 

 tide. It needs to have not only the fresh water, but the salt also, flowing over the 

 ends of its siphons. Now, the tide runs up the stream past this section, and the 

 point to be specially noted is that the Scrobicularia bed is not less than 14 feet above 

 medium high- water mark. The conclusion seems irresistible, that at the time these 

 shells lived the land was not less than 14 feet deeper in the sea than now. There 

 is something very remarkable, also, in the way in which this evidence harmonises 

 with what is found elsewhere round the shores of the Firth. Between Stirling and 

 Bridge of Allan, Dr M'Bain informs me he obtained from the brickfield specimens 

 of this same Scrobicularia, about 15 feet above high -water mark. At various 



