GEOLOGY: S. TABER 
661 
solutions it was found possible to change tiie color of the materia) by- 
adding chrome alum, and so prove experimentally that the fibers grew 
only at their base. 
The development of the fibrous structure is probably aided by small 
adjustments or slips along the surfaces of the fiber prisms and cleav- 
ages when the latter are present. 
Fibers of copper sulphate and alum are brittle and therefore diffi- 
cultly separable, but some were obtained that had a length of several 
millimeters and a thickness of less than 0.001 mm. Such fibers are 
slightly flexible and somewhat elastic. Slender acicular forms are never 
found in crystals of copper sulphate or alum that have grown normally 
in free contact with solutions, because this form is not the most stable. 
The total surface energy of one of the acicular crystals is great as 
compared with the mass, and therefore they are dissolved by solutions 
that are supersaturated with respect to more stable forms. 
Many theories^ have been advanced in explanation of the origin of 
cross-fiber veins, particularly those of chrysotile. Most of these the- 
ories presuppose the existence of open fissures in which the vein min- 
erals were deposited. It is conceivable that some cross-fiber veins 
may have been formed in pre-existing fissures, but in most cases this 
is mechanically impossible. 
Dresser^ has pointed out the absurdity of this theory as applied to 
the chrysotile deposits of southern Quebec, Canada, where the veins 
run in all directions from vertical to horizontal, occasionally reaching 
a length of 100 feet, and in places occupy over 10% of the entire rock. 
According to Pratt^ and Diller^ the chrysotile veins in the Grand Canyon, 
Arizona, over 4000 feet below the rim, extend horizontally parallel to 
the bedding of the enclosing rocks for distances of 150 feet or more. 
In many instances there is evidence that the formation of chrysotile 
veins and the alteration of the enclosing rock to form massive serpentine 
were contemporaneous processes; but the alteration of a rock to ser- 
pentine is usually accompanied by an increase in volume sufficient to 
close all appreciable openings. The lenticular shape of many veins is 
an argument against the theory of deposition in open fissures of 
mechanical origin. 
It has been suggested that chrysotile veins may have been formed 
by some process of replacement, but no one has explained why serpen- 
tine should replace serpentine of the same chemical composition. More 
over, chrysotile veins never contain pseudomorphs or show any trace 
of an inherited structure. Replacement veins are characterized by 
great irregularity in width and lack of definite boundaries, while chrys- 
