On Chlorine in Meteorie Iron. 363 
and 120°, in which directions the cleavages occur which lead to 
the tetrahedral and prismatic forms. When a fragment is thrown 
into nitric acid, a cross fracture of the main layers shows mosaic 
markings, eomptieed of bright edges and intervening depressions, 
similar in some respects to the Widmanstattian figures on polished 
surfaces of meteoric iron. The graphic character is heightened 
also by the more perfect reflexion of light from the vertical laminze 
of the thinner plates, than from their edges in the broad layers, 
which latter instantly becomea dull gray. 'The decomposition of 
the acid soon ceases, unless heat is applied, when it goes on as be- 
fore, the graphic structure remaining visible until the mass is dis- 
solved. The figures on etched meteoric iron may in part also be 
attributable to mechanical structure, instead of depending solely 
on differences in chemical composition, as heretofore imagined. 
I must remark also, that the broad cleavage surfaces of the 
cast-iron exhibit under the microscope, an exceedingly delicate, 
Striated appearance, the strize running constantly in one direction 
and being occasionally crossed by interrupted lines (either raised 
or depressed) of a larger size, at an angle of 60° and 120°; while 
from these last, other short lines or dots project at an angle of 
90°, giving rise to marks resembling the capital letter F or E. 
The specific gravity of this iron is 7.57. Its hardness is suffi- 
cient to scratch glass. It is easily shattered into fragments by a 
blow of the hammer; and on exposure to the air exfoliates almost 
Spontaneously into thin laminee. When dissolved in nitric acid, 
the carbon is left undissolved in a fine powder, showing that it 
was chemically combined with the iron, in the condition of steel. 
The structure and composition of this iron (considered along 
With that from South Carolina) appear to me to afford good rea- 
sons for concluding, that both the chemical composition and me- 
chanical structure of meteoric iron undergo alteration by con- 
tact with our earth, and that such modifications deserve to be 
considered before we attempt to employ either the one or the 
other as a characteristic of such bodies, or as the grounds of a 
theory to account for their origin. 
New Haven, May 19, 1842. 
