On Chlorine in Meteoric 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, composed 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 laminae 

 of the thinner plates, than from their edges in the broad layers, 

 which latter instantly become a 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 stri« 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 laminas. 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 rear 

 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. 



