364 The American Geologist. June, 1892 
shows the upper surface of the natural rock as it appears after 
the glacial planing, and includes a surface about five feet long. - 
The rounded forms are encased in a darker green and evidently 
somewhat chloritic, fine-grained schist, which winds about among 
the rounded masses, its fibrous structure coinciding in direction . 
with the surfaces with which it is in contact. This green schist 
cannot be distinguished from that which is common at all of the 
mines of the region and which ordinarily constitutes the country 
rock about the Tower mines. It is presumable that there are 
places in this agglomerate where this green schist is lacking, and 
the rounded masses are in absolute contact, but the drawing, 
rather hastily made, was designed to bring out the appearance of 
the pipe-shaped, calcite-filled, amygdaloidal structure, and this 
point was neglected. The rounded bodies here represented are 
not evidently of igneous rock, but rather approximate that indef- 
inite greenish rock styled porodyte by Dr. M. E. Wadsworth. 
They contain no evident free quartz,* neither do they contain 
per se anything else that is evident. They are referable to a con- 
solidated pulp made up of comminuted grains of eruptive rocks 
but having evidently a greater per centum of silica than ordinary 
basic eruptives. A few fine pyrite cubes are discoverable, and 
on being powdered the rock has a quick, slight effervescence with 
hydrochloric acid. The stones have a pale, dun-green color, are 
very fine-grained, and might, with a broadened significance to: 
that term, be called felsyte. They lack evidently the orthoclastic 
element which is essential to true felsyte. 
The most remarkable character of this singular rock is yet to 
be described, viz: About all the peripheries of these rounded 
“masses of porodyte are tubes, standing perpendicular to their 
surfaces and separated, on an average, about one-quarter of an 
inch from their neighbors. These tubes, which are normally 
filled with calcite, are sometimes more than an inch in length, but 
most frequently are less than an inch. They stand perpendicular 
to the bounding outer surfaces of the rounded masses. They do 
not enter at all, or but slightly, into the darker green schist which 
is wrapped about the masses. They are approximately circular 
or pipe-like, and their diameter is about two millimetres. Some 
of them, however, are a little zigzag, and roughened in their inner 
*In one instance a siliceous pebble, about one-eighth of an inch in 
diameter, is seen embedded in this porodyte, in specimen No. 1624. 
