HYATT: REPORT OF THE CURATOR. 
349 
Mineralogy and Geology. 
Professor Crosby reports as follows: During the early part of 
last summer the printing of Part 3 of the Geology of the Poston 
Basin was finally completed. During the remainder of the year he 
has been at work on Part 4 which embraces the Neponset Valley 
and the belt of islands extending from the mouth of the Neponset 
River in an east-nortlieast direction through Boston Harbor to 
Boston light and the outer Brewster. This well-defined linear 
group of islands lies exactly in the axis of the Neponset River and 
may be regarded as a continuation, geologically, of that valley. It 
has, therefore, seemed appropriate to designate these collectively 
“ the Neponset islands.” The field work for Part 4 is completed, 
except as there will be occasion to review special points in describ¬ 
ing and discussing previous observations; and except also the 
attention that must be periodically given to the exposures of rocks 
made in the tunnels now being driven in making the high level 
sewer through the Neponset Valley. This work affords fresh and 
continuous sections of the rocks that should not be neglected. The 
heartiest cooperation has been given by the engineers ; and during 
the year Professor Crosby has prepared a report on the geology of 
the tunnels for Mr. W. M. Brown, Chief Engineer of the Metropolitan 
Sewerage Commission, and this has been printed as a part of that 
gentleman’s annual report. 
Miss Bascom, professor of geology at Bryn Mawr, who has 
already made and published a petrographic study of the volcanic 
rocks of the Neponset Valley, is, at Professor Crosby’s request, 
now investigating also the plutonic and dike rocks which have 
unexpectedly developed many points of special petrographic and 
structural interest. Professor Crosby’s new colleague at the Insti¬ 
tute, Dr. C. H. Warren, who is a skilful petrographer, has also 
assisted him materially. A year ago Mr. M. L. Fuller undertook, 
at Professor Crosby’s suggestion, a detailed study of the glacial 
lake of the upper Neponset Valley, similar to Dr. Grabau’s study 
of Lake Bouve. This part of the work was interrupted when Mr. 
Fuller accepted a position on the U. S. Geological Survey; but he 
has now given in a very carefully prepared report on the important 
part that he has completed, and he expects this summer to be able 
to finish the whole of the chapter of Part 5 that had been assigned 
to him. 
