ANNlVEfiSAEY ADDEESS OF THE PEESIBENT. Ixix 



enter the lists with Yon Haidinger*, Baron Eeichenbaeh, Prof. 

 Lawrence Smith, and others, on the questions attending the entry of 

 these bodies into our atmosphere, and the circumstances of their 

 fall; but, considering that their surface alone is modified by these 

 conditions, he infers that their interior mass remains the same as 

 when it was wandering in space, and may to a great extent be taken 

 as a sample of the material of the planetary bodies of which they are 

 the fragments. 



Although the anhydrous silicates already so frequently named have 

 evidently been formed at an elevated temperature, it would appear 

 that such temperature was, at their origin, less high than that used 

 in the experiments. The stony portion of the meteorites in their 

 natural state is generally less perfectly crystalline than would be 

 expected of a compound which the above experiments prove to be so 

 ready, after full fusion, to form masses of a very pronounced crys- 

 talline character. And, again, the irregular figure of the grains of 

 iron disseminated in the stony matrix seems to point to the material 

 having been consohdated at a temperature below that of the fusion 

 of soft iron — a point of view which was confirmed by experiment. 



This temperature of original consolidation is a matter, of course, 

 altogether foreign to that noted at the time of fall, and existed 

 probably very long anterior to the meteorites coming into contact with 

 our atmosphere ; and the presence in a few cases of volatile sub- 

 stances in the mass proves, like a maximum thermoneter, the 

 moderate temperature of the body before it was deflected from its 

 regular course. 



Seeing how nearly the composition and structure of the meteorites 

 are reproduced by the two methods of experiment, M.Daubree refers 

 by their aid to the original mode of formation of the bodies from 

 which these meteorites come. 



If they were produced from silicated minerals by reduction, in 

 which carbon was the reducing agent, it may be objected that the 

 iron could scarcely have remained in the metallic state ; and if 

 hydrogen be supposed to have been the reducing agent, water ought 

 to have been formed at the surface, whence it appears more simple 

 and reasonable to recur to the idea of an oxidizing process. Allow 

 that silicon and the metals existed at one time in the meteorites, not 

 combined with oxygen as they now mostly are, and this by reason 

 either of too high a temperature to allow them to remain in combi- 

 nation, or of too great a separation of their particles, then, as soon as, 

 by their cooling down or by their condensation, the oxygen was able to 

 act upon the other elements, it would at once combine freely with 

 those for which it had most affinity, and if not sufficient in quantity to 

 oxidize the whole, or not enabled to act long enough, would leave a 

 metaUic residue. In fact there would be produced the silicate of 

 magnesia and iron, peridote or olivine, and gTanular portions of 

 nickehferous iron, and of sulphides and phosphides of iron. These 

 views, whilst applicable to a large proportion of the meteoric bodies, 

 would require modifications for those rarer varieties which consist 



* See Haidinger, * Phil. Mag.' November and December 1861. 



