;S The American Geologist. August, 1902 
covery of pillow-lava formed where the Snake River basalt 
ran into lake-basins.* The structure of the Newfoundland 
deposit is that expected in the deeper parts of the Hawiian aa 
flows, or may possibly be affected by as yet unknown special 
iitions of submarine extrusion by which each pillow has 
assumed the details of the pahoehoe surface. With this con- 
ception of origin there agree; the evidence of quick cooling 
with the incidental variolitism ; the extensive radial, concentric 
and irregular cracking each pillow has suffered; and the pro- 
found alteration of the lava due to the easy ingress of weather- 
ing agents along the thousands of microscopic and larger 
cracks opened up by the rapid chilling. Xext to the possession 
of their peculiar structure, the pillow-lavas described in Eur- 
ope and America have no more prominent and unvarying 
characteristic than this one of manifest, profound, metaso- 
matic alteration of the rock. 
Legends. for figures and plates. 
Plate XIV. Fig. 1. — View of Kirpon Harbor, looking northeast. The 
two prominent ridges in the upper left-hand quadrant of the view, 
occurring, respectively, on Jacques Carrier Island and Kirpon Is- 
land, are underlain by pillow-lava. 
Fig. 2. — Interior of one of the pillows, showing dark aphanitic crust, 
varioles. core of variolitic substance, and calcite matrix in which 
the pillow lies embedded. 
Plate XV. Fig. 3. — Variolite from the interior of a pillow. The scale is 
two inches long. 
Fig. 4. — Natural surface of part of a small pillow removed from its 
calcite matrix, illustrating the smoothness of the pillows and the 
vesicular structure of the outer crust. 
* Bull. U. S. Geol. Surv., No. 199, 1902, p. 113. 
