510 N. L. BOW EN 



a much simpler example of the same phenomenon. In the Palisade 

 diabase of New Jersey gravitative differentiation has taken place 

 with the result that there has been formed in the lower layers an 

 olivine-rich diabase and in the upper layers more acidic types, in 

 local patches verging upon granite. At the upper border, however, 

 a more basic phase occurs which contains a small amount of olivine 

 and represents the original magma quickly chilled and undiffer- 

 entiated. In this body of moderate dimensions all the differentiates 

 have remained in position, except that the acidic phase may be 

 injected occasionally into the more basic varieties as aplitic dikes. 

 When this occurs, the acidic phase has been noted to exert a par- 

 ticularly strong corrosive or recrystallizing action on the basic 

 phase. 



While the differentiates are of other types in the case of the 

 Adirondack complex, I believe that in a broad way the relations 

 are substantially the same, the principal complicating circumstance 

 being the prominence of reintrusion of the later liquid, the syenite. 

 The gabbro border phase I believe, with Daly and Cushing, to be 

 a chilled border, and, while this matter was not discussed in con- 

 nection with the Adirondacks, mention was made of such chilled 

 phases on page 213. In an undisturbed mass the syenite would 

 everywhere lie immediately below this basic phase if the mass had 

 also a very regular contact. However — and this brings us to 

 another of Professor Cushing's objections — if the mass had an 

 irregular upper contact, the syenite need be present only in the 

 re-entrants of the roof and need not therefore form a continuous 

 border about the anorthosite. Add to this the fact that the syenite 

 has been disturbed and re-intrusion has occurred, and I think that 

 this fact will become still more obvious. It must be confessed that 

 Professor Cushing was perhaps justified in considering a continuous 

 syenite body a necessary consequence of my hypothesis on account 

 of the diagrams that were offered in illustration of the conception. 

 But these were intended to represent in a diagrammatic way the 

 conditions under which the various types were generated, and not 

 to give a picture, except in a generalized way, of the actual distribu- 

 tion of types in the Adirondacks at present. It is recognized that 

 reintrusion of the syenite occurred, resulting in satellitic bodies 



