OF THE CARBONIFEROUS STRATA. 199 



and bromine, together with all the salts usually found in the 

 waters of the present ocean. 



The numerous trails throughout successive strata, and the 

 preservation of the habitations of such frail creatures as 

 worms, shew that the deposits took considerable time in their 

 formation and were made in great quietude. In fact every 

 thing indicates that the deposits which we have been investi- 

 gating went on from time to time with as great regularity, 

 and in very nearly the same manner, as beds of sand and mud 

 are now forming in the ordinary course of nature on and near 

 our present shores, — although we cannot well distinguish 

 regular tidal deposits, such as are now taking place. 



In bringing this dry, and I fear uninteresting, paper to a 

 close, I wish to direct the attention of my readers to the trails 

 of molluscs and the burrowings of worms now to be seen on 

 our sea shores. And for this purpose I cannot do better than 

 refer them to a charming little work of Dr. Harvey's, intituled 

 "The Sea-side Companion," and conclude with an extract 

 from it. At p. 25 of his book he says, — 



" The foot-prints of sea birds on the sands of the shore are 

 often unnoticed, and are swept away by the first returning 

 wave. So are the tracks of trailing shell-fish, which may 

 sometimes be seen furrowing the surface of fine hard sand in 

 considerable numbers. The common yellow nerite (littorina 

 littoralis) is a frequent maker of these trails, as it moves its 

 station from one small rock to another, patiently cutting a 

 road through the sands as it proceeds on its journey. These 

 marks, and the undulation left by the water on the surface, 

 where regular minute ridges of sand follow each other in an 

 orderly manner, like the furrows in a field, appear of so fuga- 

 cious a nature as to be undeserving of notice. The retreating 

 wave has left them behind, and the returning will sweep them 

 away, and all be a smooth surface again. Yet, in these fugi- 

 tive markings of the sand the geologist traces a resemblance 

 which links them with time immeasurably distant in the past 



