146 FRAGMENTS OF SCIENCE. 
destiny of the Falls of Niagara. "We may open our way to 
this subject by a few preliminary remarks upon erosion. 
Time and intensity are the main factors of geologic change, 
and they are in a certain sense convertible. A feeble force 
acting through long periods, and an intense force acting 
through short ones, may produce approximately the 
same results. To Dr. Hooker I have been indebted for 
some specimens of stones, the first examples of which were 
picked up by Mr. Hackvvorth on the shores of Lyell's bay, 
near Wellington, in New Zealand. They were described 
by Mr. Travers in the " Transactions of the New Zealand 
Institute." Unacquainted with their origin, you would 
certainly ascribe their forms to human workmanship. 
They resemble knives and spear-heads, being apparently 
chiseled off into facets, with as much attention to 
symmetry as if a tool, guided by human intelligence, 
had passed over them. But no human instrument has 
been brought to bear upon these stones. They have been 
wrought into their present shape by the wind-blown sand 
of Lyell's bay. Two winds are dominant here, and they 
in succession urged the sand against opposite sides of the 
stone; every little particle of sand chipped away its infini- 
tesimal bit of stone, and in the end sculptured these sin- 
gular forms.* 
The Sphinx of Egypt is nearly covered up by the sand 
of the desert. The neck of the Sphinx is partly cut across. 
* "These stones, which have a strong resemblance to works of 
human art, occur in great abundance, and of various sizes, from half- 
an inch to several inches in length. A large number were exhibited 
showing the various forms, which are those of wedges, knives, 
arrow-heads, etc., and all with sharp cutting edges. 
" Mr. Travers explained that, notwithstanding their artificial 
appearance, these stones were formed by the cutting action of the 
wind-driven sand, as it passed to and fro over an exposed boulder- 
bank. He gave a minute account of the manner in which the varie- 
ties of form are produced, and referred to the effect which the erosive 
action thus indicated would have on railway and other works exe- 
cuted on sandy tracts. 
"Dr. Hector stated that although, as a group, the specimens on 
the table could not well be mistaken for artificial productions, still 
the forms are so peculiar, and the edges, in a few of them, so per- 
fect, that if they were discovered associated with human works, there 
is no doubt that they would have been referred to the so-called 
'stone period.'" Kxtr acted from the Mimites of the Wellington 
Philosophical Society, February 9, 1869. 
