.388 
PROFESSOR F. D. ADAMS AND DR. J. T. NICOLSOX 
specimen of the well-known Lochseitenkalk from some locality not specified, and the 
other from the Flascherberg, near Ragatz. 
Vogt, # in his recent studies on marble, mentions cataclastic structure only in the 
marbles from a few localities along the contact zone in Velfjorden, where it was jiro- 
duced by dynamic action on the already altered limestones of the contact zone He 
states that this structure often makes the marbles of this district so brittle that they 
are unfit for use, but mentions no case in which any foliation in the marble is 
produced by the flattening of the calcite individuals. 
Cataclastic structure has been noted in a few instances in marbles from other parts 
of Europe, but it would seem to be very uncommon. The development of a foliation 
through the mechanical flattening of the calcite grains by dynamic action is, with the 
exception of the cases mentioned by Pfaff, so far as we are aware, unrecorded. 
Heim refers to this structure in certain Swiss limestones, but regards the grains as 
broken fragments. 
Twinning in the calcite of marbles is common, and has frequently been described. 
Pfaff states that it is rare except in the primitive limestones (“ Urkalken "), where 
it is always present. ZirkelI states that, as a rule, the greater proportion of the 
calcite individuals in marbles are untwinned, but that when present twinning is for 
the most part undoubtedly due to pressure and has a “ Gleitflachencharakter.” 
As, therefore, but very few dynamically altered limestones or marbles have been 
made the subject of a microscopical study sufficiently detailed to enable a comparison 
to be instituted between their structures and those seen in the artificially deformed 
limestones described in the present paper, a series of 42 limestones and marbles 
from highly folded or metamorphosed districts were selected and studied for the 
purpose of instituting such a comparison. The following is a list of the limestones 
and marbles selected, with the localities from which they were derived. The fist is 
divided into three parts—the first comprising the rocks in which the effects of the 
movements, due to dynamic action, are distinctly visible, and either closely resemble 
or are identical with those seen in the artificially deformed marbles ; the second 
embraces several mesozoic limestones from intensely folded portions of the Alps, whose 
structure is of doubtful origin ; while the third includes those rocks in which evidence 
of movement under pressure is doubtful or absent. Of the 42, as will be seen, 15 
exhibit the structures seen in the artificially deformed marbles described in this paper. 
Limestones and Marbles showing the Structures of the Artificially Deformed Marbles. 
1. Marble. Troviken, Norway. 
2. ., Tyrol, Austria. 
* 44 Der Marmor in Bezug auf seine Geologie, Btructur und seine mechanisclien Eigcnschaften, 4 Zeit. 
fur prakt. Geol.,’ Jan. und Feb., 1898. 
f 4 Lehrbueh der Petrograpliie,’ Bd. 3, p. 447. 
