C. M. Wetherill on Itacolumite. 67 
supports there is a compressive action toward the top, and a 
tensile one along the bottom of the cylinder, as in the case of 
a beam, and this gives an elliptical character to the curve. As 
the diameter of the rod increased or diminished, I should expect 
to find the curve of the stone approach the ellipse or the true 
catenary. 
The relation of itacolumite to the diamond.—The most interest- 
ing relation of this rock is to the diamond which it accompa- 
nies. This gem, found at first in the ‘‘ gurgulho” or disintegra- 
ted rock, has at length been discovered 2 setu in the itacolumite 
itself; thus showing that this sandstone is at least one of the 
sources of the diamond. 
y; 
perceived in other sandstones? It would appear that the sand 
which formed this rock contained something diffused in a regu- 
tion of its carbon. 
the mixture when sti 
re stirring, a little petroleu 
to form more readily. Th 
from, 
