On a Mass of Meteoric Iron. 
413 
An opportunity was also taken of repeating, on one of the 
polished slices, the etching with acid, to see if it was possible 
to get a more distinct display of its peculiar crystalline struc- 
ture, by watching the action of the acid on the metal. In place 
of using the mixed nitric and glacial acetic acids of the steel 
engraver, as was formerly done, nitric acid alone was used ; but 
little or no effect was produced, with the exception of a very 
slight etching on the part first touched. The nitric acid was 
then diluted with about an equal quantity of water, and on 
its being again applied to the metal a rapid action took place, 
with a considerable evolution of gas, and a brownish or dark- 
coloured matter (carbonaceous \) was seen to rise and mix with 
the acid solution, not from the coating protecting the rest of 
the metal, but from the bitten surface of the metal itself. 
Fig. 1. Fig. 2. 
Impressions of etched portions of the meteoric iron. 
The presence of this brown-coloured matter is stated not to be 
observed when ordinary steel is etched. Instead of making, 
as before, a large etched patch at the line of separation or 
fracture, of the rounded and pointed portions of the mass of 
iron, a small patch was etched near the middle of the rounded 
or lobed portion (fig. 1), and this displays very distinctly the 
characteristic and beautiful frosted-like lines of crystallization, 
crossing one another at various angles. As formerly stated, 
these lines are finer, or more minute, than in many meteoric 
irons. This finer texture seems to be also present in other 
brittle irons ; at least it is mentioned as occurring in those 
described by Professor Shepard in his Report. (See " Silli- 
man's American Journal," 1847.) I am inclined to think it 
not improbable that this fine, or less-distinctly marked texture 
