308 



observed in a detailed exploration of only four gatherings, those, name- 

 ly, from Elgin, Elchies, Lochleven, and Duddingston Loch. Nay, 

 he had found them all, except only one or two, by degrees, in the 

 Lochleven gathering alone, and a very large proportion of them in 

 each of the three others. So that, if his observations had been confined 

 to these four gatherings, or even to that of Lochleven, it would have 

 been possible to recognise and distinguish nearly all the species here 

 mentioned. 



The above list of forms is entirely exclusive of those very nume- 

 rous and varied ones, occurring, however, in many of the gatherings 

 examined by the author, as above described, which he has elsewhere 

 united together, described, and figured, under the name of Navicula 

 varians. 



The figures of Navicula elliptica, Kutz,, and its very striking 

 varieties, as the author had observed them in the study of these 

 gatherings, were referred to, in order to prove that certain species 

 vary not only in form or outline, as in the case of Navicula varians, 

 Pinnularia divergens, and many others, but also in general aspect, in 

 the number of strise in joVo^^ ^^ ^^ i^^^j comparing two frustules 

 of equal size, in the structure of the median line, and in that of the 

 central or terminal nodules. 



2. On Glacial Phenomena in Peebles and Selkirk Shires. By 

 Robert Chambers, Esq., F.R.S.E., &c. 



In this short paper, the author presented facts, from which he 

 thought himself entitled to infer that the Silurian mountain tract of 

 southern Scotland falls entirely into his views regarding ancient 

 glacial operations in the country generally, as expounded in a paper 

 read to the Royal Society of Edinburgh, in December 1852, and 

 published in the Edinburgh New Philosophical Journal for April 

 1853. He showed that the compact boulder clay, which he regards 

 as the detritus of the early and general glaciation of the country, 

 exists in the valleys of this district, and in passes amongst the hills, 

 up to those of Glenlude and Tweedshaws, which are respectively 1152 

 and 1352 feet above the mean level of the sea. Striated boulders 

 from Glenlude and Tweedshaws were brought before the Society. 

 The rounded form of the hills, and the horizontal mouldings or 

 Jlutings which are seen along the faces of many of them, he con- 



