32 The A men i-d a Geologist. January, 1896 
tier in which the sand grains are launched is, for thai locality^ 
correct. I found places where the running water had cut 
down into the sand leaving overhanging cliffs, in miniature, 
varying from :* to or more inches in bight. By pressure \ 
forced a portion of this border farther outward and, as the 
current completed the undermining, the mass slid into the 
water which bore away many of the dry grains on its surface. 
Combining Mr. Graham's observations with my own. it would 
appear that dry sand may be naturally floated in at least two 
very different ways, viz. : First, by gentle ripple waves splash- 
ing up against a sand bar having an inclination of about 
30°, as on the Connecticut river, and second, by the under- 
mining of the sand beds bordering portions of a stream, as on 
the Llano river. 
Though, as I have stated, the Llano sand was derived 
chiefly from the disintegration of granitic rocks, it effervesces 
slightly with dilute hydrochloric acid. This, however, is not 
surprising when it is known that metamorphic limestones 
also occur in this region. That granite fragments will float, 
and in a manner quite similar to this sand, I have demon- 
strated by breaking some red (Burnet or Capitol) granite in 
an iron mortar, until it had been reduced to a corresponding 
degree of fineness, and then gently sprinkling it from a paper 
onto the surface of the water. As might have been expected, 
much of it immediately sunk, but a sufficient quantity floated 
away to form a characteristic patch. Milky quartz when 
treated in a similar manner yielded even better results, as 
did orthoclase also. 
That the property of floating is by no means confined to 
the sand of any one locality or to that of any particular 
origin may he seen from an inspection of the accompanying 
table. 
How long sand will float, granting that the size and shape 
of the component grains admit of floating at all, I cannot 
say, but, should the surface of the water remain unbroken, I 
believe for an indefinite period. I base my conclusion on the 
following facts : In my laboratory I have floated sand in var- 
ious vessels for hours. In one instance, for the sake of the 
test, I allow r ed the water, with its sand, to remain for more 
than a month undisturbed. At the end of that time, as 
