DEPTHS AND DEPOSITS OF THE WEDDELL SEA. 
783 
accuracy, by reason of the occultation observations obtained during the winter, is of 
the order of one nautical mile.* During the latter period the ship was drifting in 
the ice at an average rate of four sea miles per day. As the soundings were 
practically all made within three hours of noon, none of them are likely to be distant 
from the latter position by more than one mile — that is to say, they differ by no more 
than the possible error of the ship’s noon position. 
Deposits. 
The actual samples were all abandoned when the ship was crushed. At the time 
they were collected, however, brief notes were always made, and these are quite 
sufficient to provide a short geological description. 
Everywhere in the Weddell Sea the deposit was found to be terrigenous in origin ; 
in keeping with Philippi and Pirie, the term “ Glacial Mud (and Clay) ” is therefore 
employed. Pirie rather emphasises the distinction between glacial mud and glacial 
clay ; on board the Endurance it was not thought necessary to do so, or indeed 
practicable without a detailed examination of the deposit. In the table the term 
“ Glacial Mud ” covers both muds and clays. Where the deposit was sandy, or where 
pebbles were commoner than usual, attention is drawn to these features. The origin, 
of course, of a deposit such as this glacial mud — namely, the agency of drifting ice — 
makes the presence of rocks from the size of a pebble up to boulders weighing several 
hundredweights everywhere possible. Traces of sand should also have the same 
wide distribution ; yet a deposit which could be truthfully called sand rather than 
mud was something unusual. 
In former days this characteristic deposit of Antarctic waters was classed as 
“Blue Mud.” Everything terrigenous in origin found below 100 fathoms (if not 
separated off into the small subdivisions such as Volcanic and Coral Muds) was in fact 
liable to be put down as such. This cannot have been Sir John Murray’s original 
intention, but after the publication of the Challenger volume the term certainly 
had a tendency to become almost synonymous with a deep-sea terrigenous deposit. 
For these Antarctic muds,’ however, the term was by no means a fortunate one. 
To begin with, the deposit in question characterises the continental shelf as well 
as oceanic depths. The colour, moreover (owing probably to deficiency in organic 
matter), is practically never blue, but rather dark grey or brown to brownish-grey. 
As a rule, when dried it becomes lighter in colour. Blue Mud, for these and other 
reasons detailed by Philippi, can no longer be considered a fit name. A subdivision 
of the same standing as Volcanic or Coral Mud is necessary. Philippi and Pirie 
have accordingly adopted Glacial Mud as being the most suitable term. To sum up : 
Glacial Mud differs from most terrigenous deposits in being found not only in 
shallow water ( i.e . on the shelf which in the Antarctic is 200, not 100, fathoms 
* The occultation observations have since been checked by Mr A. O. D. Crommelin of Greenwich Observatory, 
and the positions adjusted accordingly by Mr James, physicist to the Expedition. 
