1896.] Petrograp hy. 663 
Associated with the corundum in the Mysore State is a fibrolite rock. 
A tourmaline rock from the Kolar gold field in the same State and 
from North Arcot and Salem in Madras, consists of twisted and bent 
tourmaline fibres in a matrix of smaller fibres of the same substance. 
In the neighborhood of Bingera, New South Wales, two rocks are 
found as dykes cutting serpentine. One consists almost exclusively of 
green garnets and the other of picotite. The former contains also gold 
and chrysocolla. 
The Weathering of Diabase.—Mr. Merrill’ describes the changes 
that have been effected in a granular diabase at Medford, Mass., during 
its disintegration into soil. Bulk analysis of the fresh and the weath- 
ered rock yielded the following results: 
SiO, Al,O, Fe,0, FeO CaO MgO MnO K,O Na,O P,O, Ign Total 
Fresh 47.28 20.22 3.66 8.89 7.09 3.17 .77 2.16 3.94 .68 2.73—100.59 
Weathered 44.44 23.19 12.70 6.03 2.82 52 1.75 3.93 .70 3.73= 99.81 
The disintegration of the rock is accompanied by a leaching out of its 
most soluble constituents. Assuming that the alumnia has remained 
unchanged in quantity in the course of the disintegration, the percent- 
age of each constituent lost in this process is shown to be as follows: 
SiO, Al,O, FeO, FeO CaO MgO MnO KO Nao P,O, Ign 
18.03 .00 18.10 25.89 21.70 41.57 29.15 12.83 11.39 .00 
The paper is full of valuable suggestions that cannot be even referred 
to in these notes. 
Petrographical Notes.—Transitions from massive anorthosites 
into augen gneisses and into thinly foliated gneisses and transitions 
from olivine gabbro into hornblende schists are briefly described by 
Kemp* in a preliminary article on the dynamic metamorphism of 
anorthosites and related rocks in the Adirondacks. 
Pirsson® suggests the use of the word anhedron to express the mean- 
ing usually expressed in the phrase ‘hypidiomorphic form.’ An anhe- 
dron is a body with the physical constitution and properties of a crystal 
but without the crystallographic form. The term may be conveniently 
applied to the crystalline grains in rock masses. . 
7 Bull. Geol. Soc. Amer., Vol. 7, p. 349. 
8 Bull. Geol. Soc, Amer., Vol. 7, p. 488. 
9Ib., Vol. 7, p. 492. 
46 
