THE BEHAVIOR OF INCLUSIONS IN IGNEOUS MAGMAS 537 



There is yet to be examined the example in which a late member 

 of a discontinuous reaction series is added to a liquid saturated with 

 an early member. To the liquid P at 1500°, where it is just satu- 

 rated with forsterite, inclusions of cHno-enstatite are added in an 

 amount sufficient to give a total composition Q (about 20 per cent) . 

 If the temperature were kept constant equilibrium would be estab- 

 lished when the mass consisted of 4 per cent forsterite and 96 per 

 cent liquid, that is, the inclusions have been changed into the phase 

 with which the liquid is saturated and there has been an increase in 

 the amount of liquid. In order to effect this change heat would have 

 to be added to the system. If the system is self-contained, that is, 

 if the only heat available is the heat of the system itself, a cooling 

 would result and this would necessitate the crystallization of a fur- 

 ther amount of forsterite until the necessary heat was supplied by 

 this crystallization and the cooling of the mass. The net result 

 would depend entirely on the relative heats of solution of forsterite 

 and clino-enstatite in the liquid. These are probably of the same 

 order of magnitude, so that equilibrium would be established at about 

 1475° when the mass consisted of 10 per cent forsterite and 90 per 

 cent liquid approximately. The net result, then, has been the con- 

 version of the inclusions added (clino-enstatite) into the phase with 

 which the liquid is saturated (forsterite), an enrichment of the 

 liquid in the material added, with, at the same time, a pushing 

 onward of the liquid along its usual course of crystalHzation. Or it 

 could be stated that the inclusions pass into solution by precipitat- 

 ing their heat equivalent of the phase with which the liquid is satu- 

 rated.^ This, then, is the result of adding inclusions which belong 

 to a discontinuous reaction series and are later in that series than 

 the phase with which the liquid is saturated. It is sensibly the same 

 result as that obtained in the corresponding case in the continuous 

 reaction series. 



EFFECTS OF MAGMA UPON INCLUSIONS OF IGNEOUS ORIGIN 



In the paper in which the conception of the reaction series was 

 developed it was shown that these series are very prominent in rocks. 

 An attempt was made there to arrange the minerals of rocks as 



^ This is only approximately true, for equilibrium is always established at a some- 

 what lower temperature and the cooling of the mass supplies a little of the heat. 



