Meteorites mid What they Teach us. — Hensoldt. 35 
with the layers of carbonate of lime, which are indifferent to 
polarization. We also find occasionally in terrestrial rocks, 
and especially in eruptive ones, a tendency on the part of cer- 
tain crystals to gather around some nucleus and form spheri- 
cal aggregations, viz : during the process of solidification or 
cooling of a molten mass crystals will sometimes arrange 
themselves very symmetrically around some nucleus as in 
certain augite lavas of Tahiti. Again in sections of Cornish 
granites, especially of the famous luxulyanite, which is 
found in bowlders in the vale of Luxulyan, Cornwall, we 
have needle-shaped crystals of tourmaline radiating star-like 
from a common center — a marvelous object for the polariscope ; 
but all these phenomena are essentially different from those 
presented by the chondri of meteorites. 
But if from such data as these, viz., from the fact that the great 
majority of the known stone meteorites are chondritic, meteor- 
ite-investigators who are petrographers, and astronomers who 
are not petrographers, jump to the conclusion ihoX all meteor- 
ites have resulted from the accumulation of cosmic particles, 
they are in our humble opinion, greatly mistaken. That the 
true chondrites have originated in this manner is extremely 
probable and if our individual opinion is worth anything the 
writer may add that he is perfectly convinced of it. But then we 
have quite a number of stone-meteorites which are not only 
not chondritic, but which are so constituted as to preclude the 
possibility of their ever having been chondritic, and which for 
a number of other reasons cannot have resulted from an ac- 
cumulation of cosmical particles. Some of these meteorites 
have a hrecciated structure, almost identical with that of some 
of our volcanic ash-rocks and tuff's. They consist of little an- 
gular fragments, mixed with larger ones, broken crystals of 
various silicates and other detritus, exactly as we find it in 
volcanic ash-rocks. Of this class the meteorite of Petersburg 
which fell in Lincoln county, Tenn., in 1855 is an example. 
In a section prepared from this meteorite we see nothing but 
sharp fragments and grains of pyroxene, plagioclase and a va- 
riety of other minerals difficult to determine ; a number of rusty 
spots are due to limonite, which has resulted from the decom- 
position of some of the iron particles. Very similar, only a 
little coarser in structure, is the Frankfort meteorite, which 
fell in Franklin county, Alabama, in 1868. A glance at the 
