13 



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. Wads worth sev- 

 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 XL 

 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. 



