68 
The Loess of the Rhine and the Danube. [January, 
again to its former and present level, yet that the deposits 
formed beneath the waters of that ocean contain no marine 
organisms over thousands of square miles, what confidence 
can we feel in those theories that map out the continents in 
older geological periods according to the presence or absence 
of the remains of the inhabitants of the sea. The uncer- 
tainty felt respecting the latest formations fully justifies the 
large share of attention now paid to them and the efforts 
that are being made by many minds to bring the fadts within 
the range of some consistent theory. This is not a case 
where the fadts are unknown. No other formation has been 
so much studied as the quaternary. What is needed is a 
consistent theory of origin which shall violate no natural 
laws, be in harmony with the older geological record, ask 
for the aid of no unknown force, and in which every fadrt 
shall fall into its natural place and find its full explanation. 
Impressed with the importance of the question, I have 
during the last twelve years endeavoured to make myself 
thoroughly acquainted with the fadts, and have had unusual 
facilities for studying them in both hemispheres. When 
known, they appear to marshal themselves into a certain 
order, and to suggest a theory of origin that I have sup- 
ported in the pages of this journal and elsewhere, but for 
which I have not yet obtained much consideration from 
geologists. My business occupations not leaving me suffi- 
cient time to prepare a general treatise, in which the various 
questions might be fully worked out and their relations to 
each other shown, I have been obliged to present my theory 
in short essays on distinct groups of facts, and in the present 
paper I propose to take into consideration the difficult ques- 
tion of the distribution of the loess, and to show that it is 
explained by the theory that at the culmination of the 
Glacial period the ice principally occupied the ocean de- 
pressions, and blocked up the drainage of the continents as 
far as it extended. 
The loess, in the valleys of the Rhine, the Danube, and 
their tributaries, is found up to a great height above the 
present rivers. That of the Rhine is well illustrated around 
Basel, and the following section (Fig. i) is one of many 
that may be seen in that neighbourhood. It is taken on the 
right bank, where a low range of vine-clad hills comes down 
nearly to the river, about 2 miles east of the city. Quarries 
of limestone are worked in the hill-side, and fine seditions of 
the loess exposed. It is here a grey calcareous clay, of such 
a firm consistency that the workmen have excavated a 
chamber in it to keep their tools in ; and this is its general 
