314 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Ft'b. 21, 



How far this theory of the tidal current applies to the more ancient 

 geological formations of this comitry, we shall attempt to establish 

 in another letter. 



3. Notes on some Recent Foot-prints on Red Mud in Nova Scotia, 

 collected by W. B. Webster of Kentville. By Sir Charles 

 Lyell, P.G.S. 



I BEG to present to the Society some impressions of footsteps which 

 Mr. Webster has sent me, at my request, from the mud-flats of Kent- 

 ville in Nova Scotia. 



In my * Travels in North x\merica,' vol. i. p. 168. plate 7, I have 

 given a plate and description of some of these foot-prints made by 

 the sandpiper {Tringa mimita), which I saw daily running along 

 the water's edge in the Bay of Fundy. The deposit there consists 

 usually of red mud, with which the waters are charged by the under- 

 mining of cliffs of red sandstone and soft red marl. The tides rise 

 very high, and when they are lowest, large areas recently overspread 

 with red mud are laid dry, and are often baked in the sun for many 

 days, so that the mud becomes consolidated and retains permanently 

 the impressions of rain-drops, and the tracks of birds and animals 

 which walk over it. 



Mr. Webster tells me, that the divisibility of the solid mud into 

 layers arises from the deposit of each tide being separated by a layer 

 of sand or loam thrown down when the tide first rushes along the 

 bank. The sandy particles being the heaviest are first deposited, 

 and then the thin layer of mud on which the birds walk when the 

 tide recedes. On examining these specimens, I perceive that while 

 some of the foot-prints standing out in relief on the under-sides of 

 the slabs are casts of impressions made in a subjacent layer, and 

 therefore do not correspond with the imprints on the upper side, 

 some of the projecting feet-marks, on the contrary, which are almost 

 equally sharp, are formed by the forcing down of the soft mud, beneath 

 which there was a sandy layer. 



On some of the specimens will be seen the foot-print of a cat, 

 which was no doubt in pursuit of the birds, and which was w^alking 

 with its claws drawn in. In this case the weight was so great that 

 the foot has displaced several of the underlying laminse of mud and 

 sand, and has caused them to be uneven, without effacing the bird- 

 tracks previously formed there. On other specimens, worm -like 

 tracks, similar to those we often meet with on older rocks, are visible. 



Some of the specimens are in their natural state, and have remained 

 entire ; but most of them have been slightly baked in an oven by 

 Mr. Webster to enable them the better to bear their weight in tra- 

 velling. 



