H. IIENSOLDT ON FLUID CAVITIES IN METEORITES 13 



We know comparatively little of the interior of oar planet, being 

 only acquainted with a very insignificant portion of its crust; and 

 even the basic lavas, which in all probability represent the deepest 

 known regions of that crust, furnish us with but very scanty infor- 

 mation respecting the nature of the vastnesses beneath. 



But though we shall probably never be able to ascertain the 

 condition of the interior of the earth by direct observation, we are 

 in the position to say that the masses forming this interior are 

 different from those which constitute the crust. It has been 

 established that the average density of the materials which com- 

 pose the globe is 5-| times greater than that of water, but that the 

 density of the materials composing its crust is not quite three times 

 that of water. We are thus driven to the conclusion that the 

 interior portions of the globe are composed of materials having 

 twice the density of the rocks which we find at the surface. 



Now it seems to me that in the meteorites which from time to 

 time have fallen upon the earth's surface, we have been provided 

 with a most important collection of objects on which to study the 

 condition of its interior. Being the fragments of other planets, 

 they confirm in a remarkable manner those general conclusions 

 which we have been enabled to draw from undisputed facts re- 

 garding the interior of the globe. The density of by far the largest 

 number of them wonderfully coincides with that of the greater 

 portion of the globe. It has been often pointed out that the 

 interior of the earth is in all probability one vast metallic mass, 

 either liquid or solid, consisting for the greatest part of iron ; and 

 among the meteorites we have a great preponderance of iron masses, 

 while the different classes of meteoric stones represent a variety of 

 lesser depths, those which are of an essentially stony character being 

 derived from portions of the crust. 



Now, from these general remarks on meteorites, and what they 

 teach us respecting the interior of our planet, and the condition of a 

 great portion of the universe at large, I must, before concluding 

 this paper, return once more to the meteorite of Braunfels, which 

 remains the subject of our closer attention. 



I have described how a thin section shows this meteorite to be 

 composed of two materials, one crystalline and transparent, and the 

 other amorphous and opaque. The transparent material I have 

 found to be a silicate of the Phenacite group, and closely re- 

 sembling Phenacite in all its characteristics ; and the amorphous 

 substance, which so strikingly resembles iron in its pure metallic 



