A*\KREPERENCE LIST OF SUMMARIES 791 
authors, who would be glad to know also of any errors or omis- 
sison in Bulletin 86 itself. Any correspondence with reference to 
them should be addressed to C. K. Leith, Madison, Wis. 
In order that the purpose and scope of the summaries may 
be clear to every one, there is repeated below the prefatory note 
published by C. R. Van Hise with the first lot of summaries 
appearing in the JOURNAL. 
The summary proper and the comments are kept wholly separate, 
in this way preventing the confusion which frequently comes from a 
mingling of the two. In the summaries the original language of the 
author is used as far as practicable, although a single sentence may 
be taken from several sentences of the original. Where it is dis- 
advantageous to use the original language, other words are used. 
This often is necessary because the language which is adapted to com- 
plete exposition is often not the best adapted to résumé. No quota- 
tion marks are used ; for the ideas contained, whether in the original 
language or not, are wholly the ideas of the author, and the whole is in 
fact quoted.. It might be thought that better results would be reached 
by indicating through quotations what words are taken from the origi- 
nal, but this method would necessitate an unpleasant and constant alter- 
nation from quoted to non-quoted phrases. As a result of experience 
with the two methods, the editor feels certain that he is able more accu- 
rately and fully, in a brief space, to represent the ideas of the original 
author by the method proposed, than by following the usual method. 
The summaries are confined to articles or parts of articles pertain- 
ing to pre-Cambrian stratigraphy. Purely economic or petrological 
articles are not summarized unless they concern pre-Cambrian strati- 
graphy, in which case the substance of the conclusions is given, rather 
than a full account of the observations and the manner of reaching 
them. 
The abstracts have the defects of all summaries, —a certain amount 
of inaccuracy, because many modifying and qualifying facts cannot be 
given, and because undue emphasis is placed upon the conclusions. 
In many cases no comments are made. This does not imply that 
the editor agrees with the statements of the summaries. To criticise, 
qualify, or refute the statements of the authors in all cases of disagree- 
ment, would often result in extending the space taken by the com- 
ments beyond that required for the summaries. However, when the 
