russell] RECENT VOLCANOES. 41 
revolving about an axis during their flight and while still plastic, 
assumed more or less regular spherical or ellipsoidal shapes. Typical 
examples of such bombs, ranging in form from nearly perfect spheres 
to elongated oval bodies with projections or "ears" at the ends of 
the longer axis, were obtained in abundance. The central body as 
well as the projections in those examples are marked by spiral lines 
and ridges, produced by the rotation of the mass while yet hot and 
viscous or plastic. Illustrations of such forms which preserve unmis- 
takable evidence of having rotated while yet plastic are presented on 
Pis. V-VI. The bombs which most nearly approached the typical 
shapes just referred to range in size from less than an inch in length 
to masses that are 9 feet long and 12 feet in circumference in the 
center. In addition to the bombs with characteristic spherical or 
ovoid shapes, many other forms, some of them conspicuously irreg- 
ular, were noted. 
In some instances, as illustrated on PL VI, a mass of plastic lava, 
after being fired into the air and acquiring the common " foot-ball " 
shape, seems to have fallen straight downward, and the projecting 
ends or ears, being still plastic, were bent inward and perhaps flat- 
tened on the central portion of the mass. A great variety of bombs 
of this description, with recurved and infolded ears, was observed. 
Examples are also common of masses of lava which were projected 
into the air, and on falling acquired a pear-shaped or' tear-drop form.. 
These bodies, which seem to have fallen straight downward, as is indi- 
cated by their shapes, are of all sizes up to 2 feet or more in diameter. 
In many instances the tapering end is curved, or even folded down 
onto the body of the bomb, so as to produce shapes curiously like 
certain varieties of squash with curved necks These pear-shaped 
and squash-shaped bombs were in many observed instances evidentty 
still plastic when they struck the ground, as is shown not only by the 
fragments of lapilli, etc., adhering to their lower surfaces, and par- 
tially embedded in their outer crusts, but by a bulging at the base or 
flattening due to a change of shape on striking. 
In addition to the bombs with more or less symmetrical forms, due 
to masses of plastic lava cooling and stiffening while rotating in the 
air or falling from aloft, there are many irregularly shaped bodies 
which originated in a similar manner. These are frequently greatly 
elongated, loosely twisted shreds, perhaps several feet long and only a 
few inches in transverse diameter in the thickest part. One of the 
most bizarre of these irregular forms is represented on PI. VIII. This 
ram's horn-like body of dense light-colored lava measures 13 feet in 
length and 8 inches in diameter in the thickest portion. It lies on the 
west side of the highest of the Cinder Buttes, about one-third of the 
way from its base to the top, and was hurled through the air to a dis- 
tance of about one-half mile. On striking, it was still sufficiently 
plastic to become indented by the stones on which it fell, some of 
