REVIEWS 575 
thirteen years of double that of the previous sixteen years and a better- 
ment of the quality, since nearly 1,500 superior analyses are placed in 
Parts II and III of the new collection; that is, 6,471 superior analyses 
were made in the thirteen years since 1900. 
The text contains a critical discussion of the character and use of 
analyses: their representativeness, accuracy, and completeness. The 
method by which the author rated the analyses is explained. It is this 
rating, which was employed in the earlier publication, that has had 
much to do with the marked improvement in more recent analytical 
work. An inspection of the geographical distribution of the localities 
from which rocks have been analyzed shows some extensive gaps, even 
in regions accessible to petrographers, as the author points out. There 
is an important commentary on names that have been applied by 
various petrographers to divisions of the Quantitative System of Classi- 
fication, as well as a concise statement’ of the Quantitative System, and 
of the method of calculating norms from chemical analyses, besides 
numerical tables for use in the calculation. It would be a great heip to 
petrographers if this portion of the book were printed and published 
separately... The thorough indexing of the book according to four 
systems adds greatly to its usefulness. 
J. P. IppiIncs 
