No. 2.— The Squantum Tullite. 
By Rospert W. SAYLEs. 
INTRODUCTION. 
For many years the origin of the Roxbury conglomerate has been 
a matter of debate. In 1869 Prof. N. S. Shaler stated his belief in 
the marine origin of this formation (Shaler, 1869, p. 172-177). Later 
on, in his lectures he considered the conglomerate to be of glacial 
origin. In some of his published statements the same idea may be 
found (Shaler et al., 1899, p. 37-38, 57-59, 64-67). Prof. W. O. 
Crosby thought that the Roxbury conglomerate was of marine origin 
(Crosby, 1890, p. 10-17). Mr. W. W. Dodge believed in the glacial 
origin of the Roxbury conglomerate. (Dodge, 1875, p. 408-409). 
Prof. J. B. Woodworth, although not publishing his views, has often 
expressed his opinion that the conglomerate was of glacial origin. 
Prof. George R. Mansfield did not indicate any decided view as to 
the origin of the Roxbury conglomerate, but in his conclusions 
(Mansfield, 1906, p. 256-257) favored strongly the glacial idea. In 
the last paragraph of this section of his paper he says: “The great 
quantity of large pebbles of relatively fresh granite and the abun- 
dance of felspathic material in the sandstones and in the matrices 
of the conglomerates suggest that much material was furnished to 
the streams of that time by glaciers of which no direct evidence now 
exists.” 
In view of the fact that tillite of Permian age has been found in 
every continent except North America, the discovery of what appears 
to be tillite in the Roxbury conglomerate is important. Glacial beds 
of Huronian age have already been found in Canada by Prof. A. P. 
Coleman, (Coleman, 1907) and Mr. J. A. Taff (1909), has found ice- 
borne boulders in mid-Carboniferous shales in Oklahoma. 
On the 19th of December, 1909, I was gathering specimens of rock 
with Dr. Laurence La Forge, just south of Boston, for the Harvard 
Geological Museum. Dr. La Forge, who was at that time engaged in 
making a geological survey of the Boston region for the United States 
Geological Survey, had come upon a curious exposure of the Roxbury 
conglomerate at a locality in Hyde Park, across the street from the 
Becker Milling Machinery Company. The rock appeared to have all 
