J \violitic Pillow-Lava. — Daly 
69 
The radiating cracks were often seen to be widest and most 
numerous in the center of the pillow, recalling the central gap- 
ing fissures of many septaria. Such cracks are to be inter- 
preted as due to contraction of the lava in passing from the 
molten to the solid state. The outer surfaces of the pillows 
occasionally show the "bread-crust" form, and generally the 
entire surface of each pillow and the crust forming the outer 
2 cm. to 10 cm. of the mass are highly vesicular after the pat- 
tern of ordinary basalt hows. The corresponding amygdules 
are filled with calcite or, more rarelv. with chlorite, chalcedony 
Figure 3. — Diagram of strike section in pillow-lava. Jacques Cartier 
Island. Scale 1 : 25. 
or quartz. The removal of this filling material gives the other- 
wise smooth surfaces of the pillows a pitted look. The pillows 
are also similar to those of California. Minnesota, Scotland, 
the Fichtelgebirge, etc., in showing plain evidence of their 
having been once sufficiently molten to yield somewhat to the 
action of gravity. The surfaces of contact are often sympa- 
thetic, an indentation of one nicely matching a protuberance 
from the pillow adjoining. Sometimes a large, overlying pil- 
low will be seen to lie on a sort of pavement made up of a half- 
dozen'or more smaller ones flattened on their upper sides paral- 
lel to the longer axis of the larger pillow. ( Fig. 3.) The flat- 
tening of the larger pillows almost invariably causes them to 
