64 C. M. Wetherill on Itacolumite. 
Explanation of the flecibility—The flexibility of this rock is 
alcohol. 
These sections were fastened to a piece of cork in such a man- 
ner that they might be moved, and the motion observed under 
e microscope. The sections behaved alike and the play of the a 
joints was at once seen. I subsequently found that thin sections 
were not at all needed for this purpose, since the articulations 
may be perceived with the microscope in any fragment of the 
piece is fastened to the stage, which is then inverted 
and so that the projection of 
~ By observing the thin edge of the specimen regular cavities 
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4 
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parallel to the plane of stratification, one perpendicular to this " 
plane, and one perpendicular to each of the above planes. :4 
The sections were made by cementing layers of the rock upon oe 
a glass slide with shellac, rubbing down to the required thine | 
ness upon a slab of the itacolumite, and removing the resin by | 
one group engages in the cavity of — 
