196 



(letermineil at 100° and at 200°, tlie latter temperature was maintained 

 for tliree days, viz. iiiilil llie weight remained constant. 

 The result of the analysis is: 



SiO, 40.46 



MgO 40.20 



FeO 7.69 (determined as Fe,0,) 



Al,(), 4.12 



H,0 (100°) 6.14 



H,0 (200°) 1.60 



100.21 



CaO, MiiO, CrjO,, NiO are absent, as well as P,Os ; no estima- 

 tion could he made of K,0 and Na,0, because in Java platinum 

 chlorid at that time could not be obtained. In the determination 

 of tiie irou-auiount FeO and FCjO, were not estimated separately ; 

 it is likely, however, that they are both present. 



It is evident that the chemical analysis fully confirms the micro- 

 scopical examination. 



Judging from the analysis also pyroxene is probably present, 

 either separately as in so many peridotites, or in solid solution with, 

 or as a component of the serpentine. 



Presumably the latter is the case, since pyroxene has not been found 

 in any of the slides. 



It must be remend)eied that Daübhi5e") already succeeded in 

 demonstrating tiiat at a high temperature serpentine passes after 

 meltiug into olivine -j- enstatite, while water escapes : 



H,Mg,Si,0, = Mg,SiO, f MgSiO, + 2H,0. 



When lea\ ing aside the watervapour, this case is merely a sidi- 

 diviwioM of tlie system MgO — SiO,, which has been examined by 

 Andkuskn and Howen. Daubrée's experience') is in complete harmony 

 with their results; so for instance from a mixture of the system 

 MgjSiO^ — MgSiO, on cooling first Mg,SiO, crystallizes, which at 

 1557° begins to react with the solution, in consequence of which 

 MgSiO, is formed which is precipitated on the surface of the 

 olivine; at the same time the solution becomes richer in silica, so 

 that ultimately SiO, can be set free; as Daubrée added magnesia 

 he did not obtain cristobalite. In the light of later experiments his 



') DoELTER failed in this experiment. Still, it is worth virhile to peruse Daubrée's 

 carefully desciibed experiments. 



3) Gompies Rendus 1866, 1, p. 660. 



