TRANSACTIONS OF SECTION C. 495 
(2) As regards the Silurian (Lower Silurian rocks), he showed by comparison 
of sections over the North American continent (a) that the strata referable to this 
epoch swell out as they approach the eastern seaboard, and thin away, or pass into 
caleareous beds in the opposite direction. Similarly it was shown that the 
sediments of this epoch in Europe swell out westwards, and thin away, or pass 
into calcareous strata in an opposite direction, as shown by a comparison of the 
sections in the British Isles, the north-west of France, and north of Spain, with 
those of Russia. Thus, while the Lower Silurian beds of Britain and the north of 
France have a thickness of from 20,000 to 25,000 feet, in which beds of limestone 
are exceptional, those of the Baltic provinces and the shores of the Gulf of Finland 
have dwindled down to a thickness of only 1,500 feet, of which limestones, as 
shown by Professor Schmidt, form an important portion. : ‘ 
From the above comparisons the conclusion was drawn that when the Lower 
Silurian beds were being formed, the originating lands must have lain over the area 
of the Atlantic Ocean, that being the region towards which the strata swell out 
on either hand ; while the replacement of the sediments by limestone indicates the 
position of the contemporaneous oceans over Central Europe and Western America. 
(8). In a similar manner, dealing with the Carboniferous strata, the author 
showed by a comparison of sections, that over the American area the sedimentary 
strata swell out in the direction of the Atlantic shore, while they thin down or pass 
into limestones in the direction of the Rocky Mountains; so that (with one notable 
exception, that of the Weber quartzite in Nevada) both the upper and lower 
Carboniferous beds consist mainly of marine limestones in the western States, while 
their representatives of North-East America swell out into about 15,000 feet 
of strata, consisting throughout of sedimentary materials. 
Reyerting to the British Isles, the author referred to former papers in which he 
had shown how the sedimentary materials of the Carboniferous period swell out 
both towards the N.W. and 8.W. of the British Isles, while the calcareous beds 
_ thin out or are replaced in the same directions. 
From these and other considerations the author had long since inferred the 
position of the originating lands to have been to the north-west and south-west 
of the British area; and connecting this with the evidence afforded by the 
Carboniferous sediments of America, he concluded that it was one and the same’ 
Atlantic continent which had given forth the materials of which the Carboniferous 
series on either hand had been constructed. 
Thus it would appear that throughout the Archean, or Laurentian, the Lower 
Silurian, and the Carboniferous epochs, the regions of North America on the one 
hand, and of the British Isles and Western Europe were submerged, while a large 
part of the North Atlantic area existed as dry land, from the waste of which these 
great formations had been built up: and he urged that if such were the case, the 
doctrine of the permanency of oceans and continents, as tested by the case of the 
North Atlantic, falls to the ground. 
6. On the Influence of Barometric Préssure on the Discharge of Water fronv 
Springs. By Baupwin Lataam, M.Inst.C.£., F.G.8., F.R.M.S. 
In 1881, at the York meeting of the British Association, the author gave the 
result of a series of observations which he had carried on with reference to the 
influence of barometric pressure on the discharge of water from the ground, and 
he showed from the result of a series of gaugings of the periodical bourne-flow 
at Croydon, that there were certain times when the underground waters were 
influenced by barometric pressure, and that with a fall of the barometer an increase 
in the quantity of water discharged from the springs occurred. The fluctuation due 
to barometric pressure in the case of the Croydon bourne-flow at one period had 
exceeded half a million gallons per day. It was also shown from the results 
of percolating gauges, that even in a period of extreme dryness, with a rapid fall 
of the barometer, a small quantity of water passed out of the percolating gauges. 
‘Since the foregoing observations were made, the author has had an opportunity 
