Wcatlicring of Diabase in Virginia. — Watson. 365 
VI. Basalt from Kammar Bull, Bohemia. Rocks, Rock 
Weathering and Soils, N. Y., 1897; p. 223. 
\'II. Basalt from Crouzet, in the Haute Loire, France. 
Ibid. N. Y. 1897, p. 223. 
VIII. Dioryte from Albemarle County, \'irginia. Bull. 
G. S. A. 1896, 7, 357; Ibid.— N. Y. 1897, p' 225. 
This table has been compiled from all available authentic 
analyses of fresh and decomposed diabase and other closely re- 
lated rocks, and indicates the total loss for the entire rock, in 
its transformation from the fresh to the decayed state, for each 
locality given. It is significant in that it affords a ready 
means of comparing results, recorded from localities of widely 
varying latitudes, where the usual common factors employed 
in the processes of weathering are probably dififerent in ac- 
tion. /\ certain agent, or group of agents, predominating and 
rendered intense in action for one place, becomes subordinated 
in action in the transformation of the fresh rock to that of a 
residual product- — soil — for another latitude. 
The figures in each column give results on material, whose 
corresponding decomposition product varied somewhat widely 
from the original fresh rock, and in those cases where exam- 
ined consisted of a more or less incoherent mass of sand, gravel 
arid clay. Megascopically, the change was apparently com- 
plete, although in some cases, when rubbed between the fingers 
the residue was found to be gritty — due to undecomposed par- 
ticles of the original minerals. When, however, upon diges- 
tion in dilute acid and examined under the microscope, the 
decayed product revealed a greater or less abundance of the 
original minerals, in apparently fresh condition — proving that 
the change or transformation was not complete. 
This change is apparently capable of more or less definite 
chemical expression. In those cases where disintegration of 
the rock has been accomplished mainly through physical 
forces and but little effected chemically, the analyses indicate 
a small total loss for the entire rock; while, on the other hand, 
where the rock degeneration is in the nature of true decom- 
position, promoted and brought about through chemical pro- 
cesses, a proportionately large total loss is shown. Other 
things being ef|ual, the more complete the decomposition, and 
the nearer the final limit in the decay is approached, the great- 
er the total loss. 
