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18 
and the second and final one will be offered to the public, with 
both colored and uncolored figures, within a week. 
The work entitled “ The Azoic System and its Proposed Sub- 
divisions,’ noticed in the last Report of the Sturgis-Hooper 
Professor as being put in type, has now been completed and 
issued. It closes the first volume of the geological series of the 
Bulletin. This work has occupied a large amount of the time 
of the joint authors during the past three or four years. This 
was natural and necessary, since the task undertaken demanded 
the careful examination of all that had been published in this 
country and in Canada in regard to the older crystalline rocks 
of North America. A considerable amount of field-work also 
had to be done, with reference to certain important questions 
raised in connection with the undertaking. Although the 
record, as displayed in this volume, is not very flattering to 
American geologists, it is thought that the work was a necessary 
one, and that its value will be more and more appreciated as the 
discussion of the subjects here brought forward is carried on. 
Another work of importance, begun by Dr. Wadsworth sey- 
eral years ago, has been so far carried towards completion that 
the first part, comprising about 250 pages, with eight chromo- 
lithographic plates, is now in type, and will be ready for dis- 
tribution within a week or two. This work, which is entitled 
‘‘ Lithological Studies, a Description and Classification of the 
Rocks of the Cordilleras,” forms the first part of Volume XI. 
of the Memoirs of the Museum. <A few words may here be 
introduced in reference to the scope of the volume which has 
been so long in preparation. 
The close of the California Survey left among the subjects 
demanding attention the classification and description of the 
collection of rocks which had been got together from every 
part of the Cordilleran region, including Mexico and Central 
America. To these collections were afterwards added others 
from various portions of the country, the whole making up a 
mass of material of very considerable extent and value. The 
task of describing this material was intrusted to Dr. Wadsworth, 
who had already begun those investigations upon the rocks of 
Eastern Massachusetts which have been of so much importance 
in throwing light upon the geology of that obscure and difficult 
region. 
