Annual Meeting.] 
274 
[May 6. 
a very uniform rate, each complete alternation probably repre- 
senting the amount deposited in a single year ; a series of the 
colored Miocene clays from Gay Head ; a specimen of clay from 
Nomini Cliffs, Va., which last is an admirable illustration of 
joint-structure in unconsolidated deposits. There is also a vein 
of quartz in banded diorite from Algoma, Ontario, accompanied 
by faulting of the bands of the diorite. This is known to be a 
common feature of veins in the rocks but it can rarely be shown 
on a small scale in Museum specimens. 
Prof. Crosby’s time has been largely devoted to carrying out 
the plan which was outlined in last year’s report for a comprehen- 
sive and systematic representation of the geology of the Boston 
Basin. Detailed observations on both the hard rocks and the 
surface geology have been extended over the greater part of the 
basin ; and for a portion of the area the work is already com- 
pleted and in course of publication. It is proposed to publish 
this work, as fast as each natural division is completed, in the 
“Occasional Papers” of the Society under the general title of 
“ The Geology of the Boston Basin,” as described more particu- 
larly below. It will be illustrated by cuts and sections and also 
by colored maps. 
There will be, first, a series of sectional maps, on a uniform 
scale of 2400 feet to the inch, each sheet being restricted to con- 
venient and natural limits. These will necessaril}'- be somewhat 
overlapping, and will embrace the entire area of the basin. They 
will show not only the distribution and relations of the hard 
rocks, but also the superficial geology and topography, includ- 
ing the drumlins, kames, drainage lines, ponds, fresh and salt 
marshes, etc. 
Then, second, the limited areas of exceptional complexity and 
interest will be mapped on a scale of 600 feet to the inch. These 
special maps will not only show in colors the theoretical distribu- 
tion and structure of the rocks in much greater detail than the 
sectional maps, but the actually observed facts, the individual 
outcrops or ledges of the different kinds of rocks, will be printed 
in black, the aim being to make these maps very perfect com- 
binations of fact and theory. The topographic representation 
will also be more perfect, the relief features being shown by con- 
tour-lines at vertical intervals of five feet. Finally, the comple- 
tion of these detailed descriptions of the different sections of the 
