1863.] FISHEE LEXDEN BRICK-PIT. 397 



At present the River Colne meanders through flat meadow-land, 

 whose surface it is raising by the deposit of inundation -mud, so that 

 old trees are becoming buried over their butts. The bed of the river 

 reveals a layer of coarse gravel as the subsoil. On the right bank and 

 a little above the Brick-pit, a short cliff has been excavated in the 

 valley-side, where the course of the stream makes its most southern 

 elbow. A talus has been formed in the curve of the cliif, and is co- 

 vered with vegetation. A mere inspection of the place shows that the 

 area in which the Brick-pit is situated is simply a similar curve in the 

 boundary of the more ancient river- valley, where an elbow of the 

 stream which then occupied it may have encroached upon the valley- 

 side, — the bed of gravel which forms the base of the Post-pliocene 

 deposits being the former equivalent of the gravel now to be seen 

 40 feet lower in the present bed of the stream, while the old talus 

 answers to the present one. But the points of similarity do not cease 

 here ; for along the base of the present cliff are some small springs 

 issuing from the junction of the old gravel and the London Clay, which, 

 trickling down the face of the bank, have been received in a deep hole, 

 and have formed a thick bed of peat with a soft quaggy surface. A 

 short time ago a horse got mired here, and would have perished but 

 for timely aid. It is obvious that the ancient bed of peat was formed 

 in a similar manner by springs issuing from the same junction of the 

 old gravel and London Clay, which yields water abundantly through- 

 out the pit ; and that the Elephants got mired and perished there, 

 as the horse would have done without rescue the other day. This 

 explains why so many individuals have left their remains in so small 

 a space, and also accounts for the bones of the feet of an Elephant 

 being found in juxtaposition in the clay at the base of the peat *. 



I am doubtful whether the modern cliff is the result of an under- 

 mining action of the stream. Such cliffs are very noticeable when 

 they occur, but are rare in the sides of valleys among soft strata ; 

 and when they are met with, they usually present springs at their 

 bases. I believe their formation to be due to the erosive action of 

 the springs, aided by the slipping away of peat as it becomes gra- 

 dually too heavy to remain where it was formed ; and the ordinary 

 proximity of an elbow of the stream to such cliffs seems to be an 

 effect rather than a cause. Nevertheless such a rule need not be 

 general, and there appears to be evidence, in the gravel underlying 

 the talus, that the torrential action which brought it there had at 

 least its share in causing the ancient cliff in the vallej'-side. 



Both the ancient and the recent deposits of peat contain much sand 

 and gravel on the side nearest to the bank. This may have been 

 brought here on the feet of birds or other animals, or by stones rolling 

 and sand being blown down from the bank above. Both peats seem 

 to have had the effect of discharging all ferruginous colour from the 

 gravel immediately beneath them, by rendering the colouring material 

 soluble through the evolution of carbonic acid. The pebbles of flint 

 in actual contact with the peat are stained black. The ancient peat 



* These bones are uow in the Museum of Practical Geology, in Jenny n Street, 

 London. 



