Correspondence—Professor J. W. Judd. 5209 
take the beds now forming in the Black, Caspian, and Mediterranean 
Seas, and calculate their age from the sum of their thicknesses. This 
I believe has been a frequent source of error in estimating geological 
time, and it would be easy to give many illustrations of this from 
other beds. 
Thirdly, Mr. Reade supposes the denudation of sedimentary rocks 
would reduce the mean thickness. This could only be the case if 
the area of deposition were continually changing its site or increasing 
its area. It is true that any given sediment may be spread over 
a wider area than the material originally occupied (though this is 
probably only the case in fluviatile beds), but as a broad fact the 
area of the land—or denuded surface—is greater than the area of 
deposition, as we know that all sediment is thrown down near the 
shore. We must treat this question as a whole, and not take 
isolated facts. Moreover, we believe the actual area of deposition 
not only is not increasing, but, viewed on as large a scale geologically 
as we have just done geographically, remains practically the same. 
Hence every ounce of freshly denuded igneous rock swells the 
actual thickness, and no amount of redistribution can reduce it, as 
Mr. Reade seems to think. 
Supposing, lastly, that Mr. Wallace’s calculations were all wrong, 
and Mr. Reade’s curious figures (such as 5$35 = 777) all right, it 
does not touch the main point at issue, namely, the question of the 
permanency of oceanic areas. I have not yet seen a single fact that 
tells against this view. Sypney B. J. SKERTCHLY. 
THE OLIGOCENE STRATA OF THE HAMPSHIRE BASIN. 
Srr,—Your correspondent, Mr. Henry Keeping, is quite in error 
in supposing that in any remarks made at the Geological Society I 
had any desire to question the general excellence of his memory. 
The principle on which I did insist—and it is one which ] am sure 
will command the assent of all geologists—is this, that when we 
have the observations of competent investigators carefully recorded 
on the spot, these ought not to be lightly set aside in favour of other 
- observations, quoted from memory only, after an interval of thirty 
years. Under similar conditions, I should be quite as ready to dis- 
trust my own memory as I am that of your correspondent. 
The case in question stands as follows :—Webster and Lyell, in 
their accounts of Hordwell Cliff, did not notice the so-called “ Upper 
Marine Band.” It appears to have been first discovered by the late 
Mr. F. Edwards, about the year 1840. In 1846 the late Mr. Searles 
Wood, who worked in conjunction with its discoverer, gave a full 
description of the bed and described it as being clearly underlaid and 
overlaid by freshwater strata. Dr. Wright, who described the section 
in 1851, and the late Marchioness of Hastings, who published her 
final account in 1853, independently studied the section, and both of 
them assert that the marine bed was covered with freshwater strata, 
the thickness and succession of which they minutely describe. 
Now both the last-mentioned authors state that they employed 
your correspondent to assist them in exposing and measuring the 
