J. E. Marr—Paleozoic Rocks of Hof, Bavaria. 411 
Mississippi and the Hoang Ho, with less rapid rates of denudation, 
have the largest basins. The following table shows that it is the 
Mississippi, with its vast length and comparatively slight fall, that 
weighs excessively in the estimate of the average, rather than the 
Ganges or the Rhone or the Po. 
Mean rate of denudation, Excess above mean rate 
omitting the: of all seven rivers. 
Mississippi... ... asa foot per year. ...  -+0°000241 foot per year. 
Hoang Ho ... ... ssyo ne ..  —0-000118 ay 
Wppey Ganges ...° ores bp ..  —0-000053 ys 
Danube... ... .. aotcy 5 ---  —+0-000031 45 
Po, ile ae pa ...  —0-000013 x 
VITO Mme p a apes orale 9 -- —0°000002 » 
Nine ees = 0000000 
It thus appears ‘that the angi rates of denudation by ah glacial 
rivers are to a great extent neutralised by the smallness of their 
basins. And, as such rivers ought not to be left out of account, it 
seems possible that the mean rate of subaérial denudation for the 
whole land-surface of the earth may not differ very greatly from 
that obtained above, namely, one foot in about 2400 years. 
VIII.—Nores on tHe Lower Patmozorc Rocks or tHE FIcHTELGE- 
BIRGE, FRANKENWALD, AND THURINGERWALD. 
By J. E. Marr, M.A., Sec. G.S., 
St. John’s College, Cambridge. 
URING the summer I visited Hof with Professor Nicholson, 
mainly in order to examine the Graptolite-bearing shales of 
the surrounding region. These we found to be far from rich in 
fossils, and the principal fossil-bearing localities were remote from 
one another. Under such circumstances little could have been 
accomplished, but for the kindness of Herr Glass, of Hof, who 
allowed us to examine his fine collection of fossils from the district. 
To him I would tender my best thanks, as also to Prof. Geinitz, who 
not only permitted me to examine his rich collection of Graptolites 
from the Thtiringerwald preserved in the Dresden Museum, but also 
devoted some of his valuable time to me. 
For a full account of the Lower Paleozoic rocks of the region 
under consideration, I may refer to Prof. Gtimbel’s exhaustive 
«“Geognostiche Beschreibung des Fichtelgebirges mit dem Franken- 
walde und dem Westlichen Vorlande.” In that work the strata are 
grouped as under :— 
Silurian. 
Tentaculiten-Knollenkalk, 
Upper Graptolite Shales. 
Ockerkalk. 
Lower Graptolite Shales. 
Lower Silurian with Leimitz-shales, etc. 
Cambrian. 
Upper: Phycodenschichten. 
Lower: Green-grey Clay Slates. 
As Hof lies at no great distance from the Bohemian Basin, it 
might be expected that there would be considerable similarity 
