72 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



sions was a general one for the rock mass, and not limited to any one mineral. The enstatite' was found in a few cases 

 inclosed in the feldspar. 



The monoclinic pyroxene or augite is less abundant and its determination less sure than is the case with the ensta- 

 tite and feldspar. It is crossed by fissures in a very irregular manner, but shows in some cases the approximately 

 right-angled cleavage of augite. In its optical characters it resembles that mineral, but its polarization is more bril- 

 liant than that of terrestrial augite and resembles that of olivine. All the transparent minerals of the section are clearer 

 and lighter-colored than their mundane representatives, and hence tend to show in polarized light clearer and more 

 brilliant colors. The augite is not, however, so water clear as the enstatite, but has a very faint tinge of yellowish green. 

 The ferruginous inclusions are the same in this as in the enstatite. 



The determination of the olivine is more doubtful, since it only appears in small irregular grains and masses, which 

 hold a similar relation to the other minerals that the olivine of terrestrial gabbros usually does. From this and the 

 fact that optically these masses are like olivine, they are referred to that mineral. 



This stone in its mineralogical composition, its structure, bubble-bearing glass inclusions, and microlites is like 

 terrestrial eruptive rocks, and it is presumable that it had a similar origin. If the common methods of lithological 

 nomenclature were followed by the writer, it would be proper for him to give this rock a name as a rock species, but in 

 accordance with the principles of his classification he prefers to regard it as belonging to the gabbro variety (norite) of 

 basalt; for he holds to the essential unity of the universe and sees no necessity of employing different names according 

 as the rock comes from above or below. 



From the description of the mineral constituents of this meteorite it would seem that regarding the presence of the 

 feldspar Messrs. Shepard and Waltershausen were correct while Rammelsberg was not. This shows the inability of the 

 ablest mineralogical chemists to draw correct conclusions regarding the mineral constituents even of an unaltered rock. 

 The trouble seems to reside with the instrument employed; that is, with a defect in the method. Chladnite ought no 

 longer to be regarded as enstatite of the purest kind, as stated in most mineralogies, but rather as a mineral aggregate of 

 which enstatite, feldspar, and augite are the principal constituents. 



While these observations give an approximate solution of the Bishopville meteorite puzzle of twenty-seven years 

 standing, it would be well if some one having larger amounts of this meteorite at their disposal could make chemical 

 analysis of it as whole, and also analyze the minerals by the modern microscope, specific gravity, chemical method. 



Tschermak 12 . made the following observations on the meteorite: 



Bishopville is coarse grained and consists for the most part of snow-white loose enstatite. G. Rose noted also 

 still other white grains, which he, however, was not able to determine. According to my observations they belong 

 to the plagioclase element. The third constituent is magnetic pyrites. The stone has a marblelike crust, sometimes 

 colorless, sometimes black, white, bluish, and gray. The enstatite forms mostly large, but likewise small grains. On 

 one of the latter I observed sharp outlines. The section ran almost parallel to a (100). The termination of this 

 crystal was three-faced, one face answered to the zone p a, the other two, to the zones a b. The grains are interspersed 

 with many fine irregular clefts, different from the cracks which were occasioned by the mechanical preparation. Inclu- 

 sions are found only in small quantities, and consist of opaque grains, less frequently of black needles. 



The plagioclase is mostly bound up with the small enstatite grains. I nowhere observed it having a regular 

 boundary. Its outlines are roundish, ragged, or elongated. In polarized light a very distinct twin structure may 

 occasionally be seen in which either broad lamellae appear or many grains are composed of many unusually small 

 lamellae, so that they appear extremely fine lined between crossed nicols. The other grains have a single, common, 

 but undulating extinction. Many are composed of several smaller grains. The behavior in polarized light is the dis- 

 tinctive mark of plagioclase. 



An attempt to separate from the mass a few grains for further testing failed, not only because of their smallness, 

 but also for the reason that they can not be distinguished either by their color or their luster from the enstatite. 



The plagioclase shows, in places, streaks and turbidity, in which case it looks brownish in transmitted light. 

 Small opaque inclusions occur infrequently but, on the contrary, large spindle-shaped enstatite inclusions are not 

 uncommon. The magnetic pyrites forms larger and smaller grains, which are often covered with brown rust. 



Rammelsberg's analysis agrees perfectly with the microscopic characteristics of the meteorite and the content of 

 aluminum, lime, and alkalies corresponds to the observed plagioclase. G. Rose also gives a small quantity of nickel- 

 iron and a black mineral, which here and there forms the filling of fine cracks. Upon breaking them I found upon 

 such clefts a glistening armor face, such as is frequently found in the case of chondrites. 



Meunier 13 grouped the meteorite as chladnite and described its structure as follows: 



This is an extremely friable rock which consists chiefly of white lamellar material cemented together in a gray 

 groundmass and contains some black grains and others of a more or less ocherous color. The rock is formed chiefly of 

 white, opaque enstatite with a slight mixture of labradorite, nickel-iron, troilite, etc. The stone of Bishopville is distin- 

 guished first from meteorites of the common type by the nearly white color of its surface. Its fracture is irregular 

 and easily recognized. Within are inclosed many white crystals which give a porphyritic appearance. Here and 

 there little ocherous spots may be perceived, caused by oxidation of ferruginous components. Rarely, grains of a 

 yellow-bronze color resembling magnetic sulphide of iron may be seen in the mass. Finally black points occur dis- 

 seminated. The terrestrial rocks which, independent of their composition, most resemble this meteorite are certain 

 varieties of porphyritic trachytes. The disseminated crystals are all grouped together and can be separated with 



