320 The Scottish Naturalist. 



Dundee Museum drew my attention. Upon inquiry, I found 

 that it was dug up near the Albert Institute. It bears a striking 

 resemblance to the wood of the Earn beds, with which I could 

 not help associating it: 



The red and blue bed of clay is much older than the haugh 

 •deposit, being related, I think, to the Enrol beds. I should not, 

 I fear, have represented it as overlying the boulder clay, it being 

 an earlier (estuarine ?) deposit. Its contortions may have re- 

 sulted from the pressure of moving ice above. It is, however, 

 entirely free from ice-blocks or positive disturbance ; but it is 

 impossible to say how much of it has been removed, seeing 

 that even now the river is removing, from 1 2 feet above to the 

 bottom of the stream, 20 feet or more of this deposit. It must 

 not be forgotten that the river has been constantly cutting itself 

 a lower channel, ever since it first began to work upon the 

 glacial debris. 



In the transverse section of the valley (Plate IV.) the figures 

 refer as follows : — 1, Old Red Sandstone, dipping towards the 

 north ; 2, Boulder Clay ; 3, Higher Haugh, or rearranged 

 glacial material ; 4, the Red and Blue Clay that ought perhaps 

 to underly (in section) the Boulder Clay; 5, Lower Haugh; 

 and 6, the River. 



Very little is said about the Earn valley in this paper. 

 Much more might be said, but I know not whether I may have 

 an opportunity of making further observations. 



N.B. — By a most untoward accident, the rule — line 14, page 266 — was 

 inversely stated. It was, however, I doubt not, easily corrected by every 

 reader. It should be : — The river denudes the outer bank of a curve and 

 restores the inner. 



That the shifting of the river is sometimes a rapid process, further evi- 

 dence is adduced. In a map of the Basin of the Tay, dated 1S31, by James 

 Knox, the dead-water D is indicated only by a bend in the stream at its 

 western extremity, so that the river crept over an immense piece of land, 

 wrapping the whole of the north side of D, between the years 1 83 1 and 

 1845, wnen the circle was completed and the water broke through, leaving 

 the dead-water which has since filled up. B seems to be indicated by a 

 bend in the stream to the north. This dead-water may also have been 

 formed and cut off since 1831. Other movements are indicated. The 

 Caledonian Railway Coy. should look to Forgan Bridge, for in the effort 

 to protect the central iron columns, the bed of the stream has been filled 

 with trap, which has caused a pebble-bed to accumulate: This is throw- 

 ing the water on to the west bank, which is rapidly going, and the line 

 being ncared. 



