AN-NIVEESAET ADDEESS OP THE PEESIDENT. Ixxiii 



air, the iron oxidizes, as well as certain other bodies associated with 

 it, and especially silicon. This oxidation gives birth to a ferruginous 

 silicate, which forms the upper part of the metallic bath. It is a 

 true liquid scoria, which by coohng may become pasty and then 

 solid, and will present in the latter state a stony, crystalline structure, 

 entirely different from the spongj^, cellular substances which have 

 been termed volcanic scoriae. Such is the metallurgical sense in which 

 the scorification of the globe is intended to be understood. 



The materials thus affected to a considerable depth may, even at 

 the present time, exhibit, according to their depth, masses in the 

 three conditions above named — the solid, pasty, and fluid. 



Native iron, so generally a constituent of the meteorites, is want- 

 ing, it is true, in our terrestrial rocks ; but the explanation is to be 

 found in the complete union with oxygen to which that metal is 

 prone. And, considering the comparatively small mass of the eruptive 

 rocks open to our investigation, it seems probable that with increasing 

 depth a corresponding difference of composition would appear. Thus, 

 beneath the lavas of Iceland, analogous to the meteorite of Juvinas, 

 and beneath our peridotic rocks, like that of Chassigny, it is likely 

 that there occur masses of Iherzolite rock in which native iron 

 similar to that which occurs in the meteorites of the common type 

 begins to appear, and that at still greater depths we should have 

 types more and more rich in iron, of increasing density, until they 

 would at length only be paralleled by the native iron. 



The occurrence of platinum tends to confirm these views. This 

 metal, of extreme density, which ought upon such a supposition, 

 until erupted, to occupy a very deep position, is commonly associated 

 with native iron. And in the Ural it has been found encrusted with 

 chromic iron, and even with fragments of serpentine, lending a new 

 support to the idea of the existence at great depths of magnesian 

 rocks of the peridote family. 



Lastly, it is observable that the meteorites never contain minerals 

 similar to the material of our stratified rocks. Haidinger has lately 

 observed*, "The minerals composing granite, gneiss, mica-schist, 

 and others representing the most solid basis of the terrestrial crust 

 are wanting in them ; and, to name a particularly important species, 

 they are totally destitute of pure silica or quartz " f. Yarious reasons 

 may be assigned for this remarkable fact. It is very generally 

 allowed that the crystallization of these minerals, and particularly 

 of the felspar group, has not been accomplished by simple fusion, 

 but has needed the aid of other agents, and especially of water. 

 Hence it may be suggested, either that the meteorites which impinge 

 on the surface of our earth are fragments of the internal parts of 

 planetary bodies formed like our own globe, or that such planetary 

 bodies are themselves deficient in quartziferous and acid silicates, 

 and in stratified rocks. And we might further infer that they have 

 not witnessed the cycle of events which in our own planet have in- 



* " On the original Formation of Aerolites," Phil. Mag. 1861. 

 t A single but notable exception is the occurrence, shown by Gustav Eose, of 

 quartz in isolated crystals in the meteoric iron of Toluca. 



