T. Mellard Reade—Age of the Earth. 309 
a foot in diameter down to bits an inch across. They are subangular 
and stand out by weathering as if they were composed of harder 
material than the matrix in which they are imbedded. But when 
we apply the above-mentioned test, we find that this must be referred 
to one of the masses brecciated in place. As shown in the accompany- 
ing sketch, the larger and smaller fragments are packed in between 
the joints in such a manner as to prove conclusively that they are 
not the tumultuous accumulation of a shore deposit; for the flat 
sides of the pieces are commonly continuous in the same direction 
and agree with observed joints by which their limits and position are, 
obviously determined. A close examination soon shows that kind of 
weathering along the joint planes which we see in the striped 
Silurian rock known as the Moughten Whetstone, found near Aust- 
wich in the Craven district, or in some of the banded flints so common 
over the south of England, where the rounding off of the corners 
is seen to be due to the mode of weathering. I take it therefore 
that the brecciated bed in the Dimetian of Brynygarn is not of 
transport origin, but represents brecciation in place and subsequent 
weathering along the joint planes. : 
VI.— Examination oF a CancuLaTion or THE AGE oF THE EartH 
BASED UPON THE HypoTHEsis OF THE PERMANENCE OF OCEANS 
AND CONTINENTS. 
By T. Metuarp Reape, F.G.S8. 
OME views in theoretical geology are held so vaguely that when 
one attempts to grasp them it is like clutching at shadows. To 
any one who will put his ideas into figures our thanks are therefore due. 
Mr. Wallace, in “Island Life,” ! has treated us to a calculation of 
the Age of the Earth based upon the hypothesis now becoming 
fashionable of the “ Permanence of Oceans and Continents.” It is 
my intention now to examine into the validity of the figures he gives 
and the light they throw upon the idea he so strenuously maintains. 
The nature of the calculation is this :—He accepts Prof. Haughton’s 
estimate of the maximum thickness of the sedimentary. rocks at 
177,200 feet, assumes that all the denuded matter from the land area 
of the world, taken at 57 million square miles, is laid down upon a 
coast-line 100,000 miles long and 380 miles wide, and infers that as 
the area of deposit to that of denudation is in that case as 1 to 19, 
that the vertical accumulation of sediment will be nineteen times as 
rapid as its removal from the land. The denudation he takes at the 
1 Tsland Life, pp. 214—216. He says: ‘‘ If therefore we take a width of thirty 
miles along the whole coast-line of the globe as representing the area over which 
deposits are forming, corresponding to the maximum thickness as measured by geolo- 
gists, we shall certainly over—rather than under—estimate the possible rate of deposit. 
Now a coast-line of 100,000 miles with a width of 30 gives an area of 3,000,000 
square miles on which the denuded matter of the whole land-area of 57,000,000 
square miles is deposited. As these two areas are as 1 to 19, it follows that deposi- 
tion, as measured by maximum thickness, goes on at least nineteen times as fast as 
denudation—probably very much faster. But the mean rate of denudation over the 
whole earth is about one foot in three thousand years ; therefore the rate of maximum 
deposition will be at least 19 feet in the same time ; and as the total maximum thick- 
ness of all the stratified rocks of the globe is, according to Professor Haughton, 177,200 
feet, the time required to produce this thickness of rock, at the present rate of denu- 
dation and deposition, is only 28,000,000 years.” 
