454 THE GEOLOGIST. 
with a great approach to accuracy, and, moreover, that this chord might b( ! 
easily dra^n on his diagram, because twenty-seven, i. e., ten and seventeen ■. 
being also equal to three times nine ; it is extremely easy to divide the circle . 
in the manner required by using its radius in the ordinary way. A diametei * 
bisecting this chord at right angles, and drawn to the supposed centre of the j 
water-hemisphere, forty-three degrees south latitude, necessarily passes both i 
through the geometrical centre of the earth, and through its centre of gravity, i 
As the basis of this construction of the diagram, it was assumed that the two i 
constituent areas of the earth's surface, consisting of land and water, are as i 
the squares of the arcs by which they are bounded. I 
The author briefly controverted the statements of Peterman and Sir John 1 
Herschell, who ascribe the appearance in question to " tumefaction," or the j 
" superior intensity of the causes of elevation in northern latitudes, and in i 
former geological epochs," observing that if earthquakes and volcanos are evi- - 
deuces of such superior intensity, the elevated land ought to be on the oppo- 1 
site side of the globe, since the volcanos are three times more numerous in the 1 
water than in the land-hemispheres. He wished to ground his speculations on I 
existing facts, and regarded them as proofs that as one haK of the moon is i 
probably heavier than the other h^, so the earth is heavier on the water- than i 
on the land-side. He supposed the greater weight on the water-side to be ! 
produced partly by an excess of mineral veins, beds of ironstones, and basaltic j 
rocks, with others of high specific gravity on that side, and partly by an excess i 
of hollows and cavities filled with water on the other side. Hence would 
result the conclusion, admitted by Sir J. Herschell, that the earth's centre of 
gravity is different from its centre of form, or geometrical centre. The author 
was proceeding to show how the amount of this eccentricity might be computed 
with some approach to accuracy, but the President expressed the opinion, in 
which the author cheerfully concurred, that a subject, the treatment of which 
required so much of mathematical demonstration, was better adapted to be 
pursued in another section. 
Besides the diagram already referred to, the author showed another contain- 
ing a list of ten of the highest mountains dispersed through the land-hemi- 
sphere, and of ten dispersed in like manner through the water-hemisphere, for 
the purpose of illustrating the fact that the mountains of the land-hemisphere 
are uniformly of a much greater elevation above the sea-level than those of the 
water-hemisphere. The heights of all these mountains were given in metres. 
The sums of the heights of the one group and of the other, by striking off 
a cypher at the end of each, gave the average heights of the mountains in each 
group. Regarding them as gauges for measuring the depth of the ocean, and 
presuming that the mountains, which rise above submerged continents in the 
water-hemisphere, and present their summits in the form of innumerable islands, 
are, generally speaking, and relatively to the solid sphere of the earth, equal in 
elevation to the mountains of the land-hemisphere, tlie author drew the con- 
clusion that the general depth of the ocean (its central portion) may be taken 
as approaching to two kilometres, and that the depths much exceeding this 
must be attributed to local disturbance. 
ON ISOMETRIC LINES, AND THE RELATIVE DISTRIBUTION OF 
THE CALCAREOUS AND SEDIMENTARY STRATA OF THE CAR- 
BONIFEROUS ROCKS OF BRITAIN. 
By Edward Hull. 
As it is intended that this paper shall be laid before the Geological Society of 
London, only a short abstract can be presented here. 
The author endeavoured to show that during the Carboniferous period a barrier 
