DR THOMSON ON THE STRATA OF BERWICKSHIRE. 85 



birds busily engaged about the brink where the nest was placed, and, 

 when near enough, he clearly perceived that they were adding, with 

 all possible dispatch, fresh materials, to raise the fabric beyond the 

 level of the increased contents of the pond, and that the eggs had by 

 some means been removed from the nest by the birds, and were then 

 deposited upon the grass, about a foot or more from the margin of the 

 water. He watched them for some time, and saw the nest rapidly 

 increase in height, but, I regret to add, that he did not remain long 

 enough (fearing he might create alarm) to witness the interesting act 

 of the replacing of the eggs, which must have been effected shortly 

 afterwards ; for upon his return, in less than an hour, he found the 

 hen quietly sitting upon them in the newly-raised nest. In a few days 

 afterwards, the young were hatched, and, as usual, soon qiiitted the 

 nest, and took to the water with their parents. The nest was shewn 

 to me in situ very soon afterwards, and I could then plainly discern 

 the formation of the new with the older part of the fabric. 



Observations on the Strata of Berwickshire and North Durham. By 

 EoBERT D. Thomson, M. D. 



The Edinburgh coal-beds which have recently attracted so much 

 attention, in consequence of the discovery in their most ancient ele- 

 ments of several remarkable fossil fish, are interrupted, in their 

 continuity southwards, by the Lammermuir range, and again appear 

 on the banks of the Tweed, along the southern boundary of the Merse. 

 Now, the great problem requiring solution is, What is the age of the 

 Berwickshire strata, which occupy the interval between the Edinburgh 

 and Northumberland coal-beds ? In a former paper, which I read 

 before this Club soon after its institution, and which was subsequently 

 published, I described the central part of this county, including, in my 

 observations, particularly what I termed the New Red Sandstone for- 

 mation, which comprehends by far the greater portion of the Merse, 

 and was therefore well deserving of an attentive consideration. My 

 object was simply to describe the rock as it was presented to me during 

 a very careful examination, more especially within the limits to which 

 I then confined myself ; and I adopted this name, first, because it had 

 previously been applied to this formation in this particular locality, 

 both by Mr Smith and Mr Greenough, in their respective geological 

 maps of England ; and, second, because I considered the facts which I 

 had accumulated were sufficiently strong in favour of the idea, that 

 this designation had been correctly applied by these geologists. For, 

 according to the general notions which prevailed, relative to the 

 position of the new red sandstone, it was held by geologists, that the 

 sandstone which lay over magnesian limestone belonged to this forma- 

 tion, the magnesian limestone itself being superior to the carboniferous 



