THE BEHAVIOR OF INCLUSIONS IN IGNEOUS MAGMAS 531 



a part of the general liquid, their melting being accomplished by- 

 precipitation of more basic plagioclase. 



Summing up the result of adding to a liquid various members of 

 a solid solution series with which it is saturated we find that if the 

 added inclusion is nearer the high temperature end of the series than 

 the crystals with which the liquid is saturated the reaction is such as 

 to decrease the amount of liquid and is exothermic. If the inclusion 

 is nearer the low-temperature end of the series than the crystals 

 with which the liquid is saturated, the reaction is such as to increase 

 slightly the amount of liquid and is endothermic. The liquid, too, 

 is enriched in this case in the constituents of the low-temperature 

 end of the crystallization series. Even inclusions consisting of the 

 precise crystals with which the liquid is in equihbrium must react 

 with the liquid as the temperature falls. 



Whatever the composition of the inclusions, then, the liquid may 

 show very marked effects upon them even though it is saturated, 

 and consequently such effects would not constitute evidence of 

 superheat. A little consideration will show, too, that these reac- 

 tions have no significant effect upon the course of the liquid. Re- 

 garding the progress of the liquid as resulting from fractional 

 crystallization, the liquid will in all cases run along the boundary 

 curve {ED) as the temperature falls. The point it will eventually 

 reach on this curve will depend upon the perfection of fractionation 

 which in turn depends upon the rate of cooling. Inclusions of the 

 more calcic kind tend to limit the career of the liquid by using it up, 

 but at the same time furnish heat that tends to slow up the rate of 

 cooling. Inclusions of the more sodic kind tend to push the liquid 

 onward upon its course of crystallization, but hasten the cooling. 

 The original unaffected liquid has all the differentiation potentialities 

 that the liquid has after entering into the reactions mentioned. 



REACTION SERIES 



In the discussion relative to liquids of the diopside : anorthite : 

 albite system nothing has been said regarding the effect of adding 

 solid diopside to liquids saturated with diopside for the reason that 

 there is no effect. The solid diopside simply remains as such on 

 account of its being a pure compound of definite composition. But 



