314 The American Geologist. NoTember, i<joo 
It was, a few years ago, sawed in two for me by the Chester 
-Granite Co., and the interior was found to be a beautiful un- 
dulating coarse drusy surface of fine pale amethysts. 
3. An Emery and Iro?i Stalagmite. 
Figure '.\. 
The object figured had the shape of the thorn from a rose 
bush, which had been separated from the branch so that the 
base is concave from the shape of the twig on which it grew. 
It was taken from an iron supporting rod beneath a high 
speed emery wheel in the United States Arsenal, at Spring- 
field, used in polishing down some portion of a rifle barrel, 
and was formed at the point where a stream of sparks was di- 
rected against the cylindrical iron support of the machine. 
Now and then a grain of emery torn off with a minute por- 
tion of highly heated iron attached, struck the point just so 
that the iron welded itself to the point of the stalactite-like 
form. This is more remote from ordinary geological processes 
than the others, but illustrates how the icicle or stalactite form 
depends on action concentrated on a growing point. 
The point is seven inches long and has a curious concen- 
tric structure in cylinders which are almost separate from each 
other and which terminate in regular succession and thus pro- 
duce the regular tapering form. They are so exceedingly thin 
and so entirely separate that several have broken away near 
the point, destroying the perfect symmetry of the original. 
4. Rytlimiral erosion. 
rif,Mire 4. 
Some years ago, a pebble of a medium grained red sand- 
stone, an average brown stone, was brought me which had 
been taken from the bottom of a well, excavated in sandstone 
for the placing of a turbine wheel at the pistol shop iti Hat- 
field, Mass. 
The boulder has as perfect a surface as a sea beach pebble. 
It is 9 inches long and 3 wide in the thickest part. It is not 
known how long it had been in the narrow space between the 
wheel and the bottom of the well. It tapers at one end to a 
flat chisel-like edge, like that of an Indian adze, and narrows 
at the other to a similar edge wdiich makes an angle of about 
