430 Proceedings of the Royal Physical Society. 



is cut off to the eastward, where the overlying bed of sandy 

 clay, and the lower bed of marine sand are observed to come 

 in contact. This protuberance of sand and gravel extends 

 towards the centre of the sand-pit, where a depression oc- 

 curs which has been filled up with humus. This short lateral 

 ridge of sand and gravel presents an appearance similar to 

 what is formed by the bifurcation of .rivers, or by currents 

 heaping up deposits along their margins. The uppermost bed 

 of sandy clay, which forms part of the so-called stratified 

 marine silt, has all the characters of a marsh silt or lacustrine 

 deposit ; and the neighbouring hollow indicates the existence 

 of a former lake. This is still a marsh, over which the Water 

 of Leith occasionally flows as far as the Bonnington road ; 

 although the river is now confined within narrower limits, and 

 guided by piers across the extensive foreshore of flat sand to 

 its junction with the sea. 



IV. On the Danger of Hasty Generalization in Geology ; with Special 

 Reference to the so-called Raised Sea-Beach at Leith. By 

 Alexander Bryson, Esq., F.R.S.E. 



As my friend Dr M'Bain was to favour us with a com- 

 munication on this subject this evening, I thought it might 

 interest the Society to add, as a sequel to his observations, a 

 few notes, some of which were formerly brought by me before 

 the Eoyal Society here. 



It is proper, before alluding to the failings of our friends 

 in making hasty generalizations, to confess our own failures, 

 so that by plucking out the beams from our own we more 

 readily detect the motes in our neighbours' eyes. The first 

 instance which I shall notice of erroneous conclusions, drawn 

 from scanty data, occurred to myself in 1856. Our late 

 lamented fellow, Dr Fleming, brought me one day a very 

 beautiful specimen of Carrara marble, on which was exhibited 

 the most decided marks of a fossil plant, and, being much 

 engaged at that time in the microscopic study of the Carboni- 

 ferous flora, I felt no hesitation in pronouncing it to be a true 

 Stigmaria. This being a new fact in geology, of course the 

 specimen was often exhibited to demonstrate the existence of 



