204 O. A. Derby—flexibility of Itacolumite. 
t 
course of the Rio Verde, one of the headwaters of the Rio 
Grande branch of the ‘Parana, in the mountainous plateau 
lying to the westward of the Mantiqueira. The cuttings are 
mainly through gneiss, in great part decomposed, but at 
several points narrow belts of itacolumite are also cut through. 
At a place called Jurumirim, the river and railroad pass by a 
short, narrow gorge through a high ridge of itacolumite ex- 
n the sides of this gorge the 
specimens. ‘This locality is about fifty miles southwest of Sao 
formation has been traced continuously to and beyond the 
Serra de Itacolumi at Ouro Preto. Though the intervening 
region has never been examined, there can be little doubt that 
the beds here examined are identical and continuous with those 
of Sao Joao D’el Rei and Ouro Preto. 
This cutting exposed very clearly the rock in its natural 
state and as affected by percolating waters and surface agencies. 
The total thickness of the itacolumite series in the range of 
along the numerous joints, and it is difficult to find masses that 
can with certainty be pronounced to be in their original state. 
a beds strike N. 60° E., and dip to the N.W. at an angle 
of 30°. 
by fissures and stratification planes, massive and schistose, com- 
pact and friable, non-flexible and flexible portions may be 
found within a distance of a few centimeters, and in exactly 
the same relative position in the bed. Several such masses were 
observed, of which one is represented in the following figure. 
