92 Reports & Proceedings—Edinburgh Geological Society. 
with the conflicting waves of a choppy sea. Were, he asked, the 
smallest of these of the nature of eddies swirling on the larger waves ? 
There was a reference to the origin of Mr. Tiddeman’s “ reetf- 
knolls ’, the mystery of which would, he hoped, be cleared up by 
Yorkshire geologists. 
The address concluded by referring to various matters geological 
and physiographical,and concluded withthe geographical distribution 
of organisms which were more or less dependent upon the character 
of the rigid block. . 
EDINBURGH GEOLOGICAL SOCIETY. 
Mr. E. B. Bailey, M.C.,B.A., F.G.S., F.R.S.E., President, in the chair. 
1. “‘ A new Voleanic Vent and other new Geological Features on 
the Shore, Weak Law, Gullane.’ By T. Cuthbert Day, F.CS., 
F.R.S.E. 
The place referred to is a wild, rocky stretch of coast, about half 
a mile in extent, a little to the west of the Island and lighthouse of 
Fidra. The author demonstrated by means of a map and lantern 
views the geological structure of the shore. Summing up the work 
commenced in 1914 and continued in 1919 and 1920, he sought to 
establish the presence on the shore at Weak Law of the following 
features:—(1) A considerable fault running along the shore 
from 8.W. to N.E. with a downthrow to the N.W. of 200 feet 
or more. This fault brings down the Carboniferous shales 
of a considerably higher horizon to the level of the lowest 
bed on the shore, which is a nearly horizontal flow of a very 
vesicular trachyte lava. This lava is itself visibly overlaid by 
trachyte tuff and trachyte lavas to the height of 50 feet at least in 
the cliffs. (2) A great mass of intrusive igneous material, the matrix 
of which appears to be composed of white trap; the whole intrusion 
is highly charged with fragments and blocks, particularly of shale 
and ironstone. This intrusive mass fills the line of fault, cementing 
itself to both sides, and sending extensive tongues into the trachytes 
of the shore. (3) A sill of white trap in the shales, near low-water 
mark, and connected with the main intrusion. (4) A small intrusive 
boss of trachyte piercing the trachyte lava of the shore. It is of 
different material to that of the lava, being very compact and 
showing many decomposed phenocrysts of sanidine and a great 
number of scattered granules of augite. (5) A volcanic vent, about 
230 yards in diameter, breaking through the older trachyte rocks 
of the shore, and itself subsequently truncated by the fault before- 
mentioned, and invaded by the intrusion filling that fault. The 
presence of this vent was shown by the following evidence: A 
boundary-line can very readily be traced ; the lavas and tuffs outside 
the boundary dip inwards towards the vent. The ash within the 
vent is everywhere essentially different to that found outside, a 
characteristic feature being that it is highly charged with dolomite 
