434 
CROSS. 
That the brecciated mass, whatever its condition when 
fractured, became plastic to a certain degree during the 
subsequent splierulitic growth, is clear. In the first place, 
the symmetry of these huge spherulites, several feet in di¬ 
ameter, cannot be explained on the assumption that they 
are entirely secondary devitrification products of a solid 
glass. Some force was able to control the growth of the 
delicate branching arms of the earlier crystallization and 
limit it to a certain relationship to the outer form. That 
these arms were produced by rapid crystallization in a 
viscous medium seems an irresistible conclusion from the 
synthetic experiments mentioned. In harmony with this 
idea is the fact that microlites and minute garnet crystals 
of an earlier formation are strongly resorbed in the denser 
spherulitic growth, and less so in the succeeding coarser one; 
but perhaps the strongest evidence of a plasticity within the 
area of crystallization is afforded by a feature of certain 
spherulites which will now be described. 
Fractured faces normal to the circumference of large 
spherulites often show what appear to be veins, a centimeter 
or less in width, cutting sharply through the fragments of 
the breccia. Examination shows that these vein-like spaces 
extend into the spherulite for varying distances from the 
circumference to which they are nearly at right-angles; that 
they curve and branch laterally, and generally die out to¬ 
ward the center. They are filled with a mixture of micro¬ 
pegmatite spherulites and an irregular aggregate of quartz 
and feldspar grains. Some of them contain very minute 
and delicate litliophysal cavities, with several concentric 
shells. Further, these apparent veins do not cut across the 
fibrous growths, and it seems even clear that, in some way, 
these spaces were marked out and occupied by plastic matter 
when the adjoining fibrous parts of the spherulite were 
formed. This is indicated by the fact that the smooth sur¬ 
face bounding the radiate growths against the vein area is 
beautifully fluted, the undulations corresponding to concen¬ 
tric zones of the spherulite. Figure 2, Plate 6, represents 
