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 Bennington 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 Koyal 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 
