Meteorites ayid What they Teach us. — Ilensoldt. 77 
world after Hahn's ludicrous fiasco. He has simply discov- 
ered fluid enclosures in the sections of at least three meteor- 
ites, minute cavities, filled with a liquid such as we find in 
abundance in terrestrial rocks. This may seem a very trifling 
matter, but we shall soon see that its significance is very 
great. 
There is nothing more common in terrestrial minerals than 
httle enclosures of fluid. If we prepare a thin section from 
one of the whitish quartz-pebbles to be found in every river- 
bed or gravel deposit and examine it under the microscope 
with a low magnification, we observe the whole field crowded 
with minute dust-like particles like a sort of cloud. Now if 
we increase the magnification these dots will enlarge in pro- 
portion to the power employed till each expands into a well- 
defined cell or cavity, in the interior of which a round object 
is seen constantly moving about. These cell-like objects are 
cavities filled with a liquid and the moving body in each is a 
bubble which is perpetually altering its position. In the 
largest of the cavities the motion is barely perceptible, but in 
the smaller ones it is quite lively, the bubbles darting rapidly 
from one side of the cell wall to the other. Now what causes 
the white appearance of the so-called milky quartz? Some 
coloring-principle, one would naturally conclude. Nothing of 
the kind ; the white color is entirely owing to the presence of 
countless millions of fluid enclosures. The cavities do not 
imprison a white liquid ; the white color is merely an optical 
phenomenon due to the reflection of the light, by the myriad 
walls of the cavities. We have exactly the same thing in snow, 
which is not white by virtue of a color ; if we melt it we get 
the clear water of which it is composed. 
Before we return to our meteorites a few observations on 
the cause of this })erpetual motion may not be out of place. 
This bubble-movement has nothing to do with "Brownian" 
motion. In the latter we have minute solid particles driven 
about by molecular currents in a liquid. If, for instance, we 
dissolve a little Indian ink or gamboge in water and examine 
a drop of this under a "quarter" or "sixth" objective, we are 
startled to behold a very lively motion of the minute particles, 
a motion which never ceases till the drop has evaporated, 
and if we were to enclose it in an air-tight cell it would con- 
tinue for years, or centurie.-^ for that matter. This is Brown- 
