NEPHELINE-BEARING ROCKS. 185 



to that on the periphery of the phenocrysts. There are 

 also, interstitially, patches of minute plagioclase laths with 

 ophitic green pyroxene. This feature also is exhibited in 

 some of the northern rocks. There are a few large patches 

 of a zeolite of moderate birefringence. This rock is clearly 

 an essexite. A second rock from the same locality and 

 occurrence differs in the almost complete absence of ortho- 

 clase. The plagioclase is labradorite, and there is a little 

 yellowish interstitial material with minute felspar laths 

 and augite of the second generation ; apatite is rare. 

 This is an olivine dolerite. It is possible, of course, that 

 the essexite is not a distinct occurrence, but that the section 

 examined chanced to pass through a locality of orthoclase 

 segregation in the essexitic dolerite. 



It will be seen that the specimens bear features strongly 

 recalling the northern rocks and may be considered to belong 

 to the same series. Their intrusive character into Tertiary 

 basalts supports Mr. Wilkinson's statement that the latter 

 overlie these at Stewart's Brook. The extreme coarseness 

 of grain of the majority of the rocks makes it in the highest 

 degree improbable that they were flows. Might it not be 

 suggested that they will be found to form sills in the Ter- 

 tiary basalt, and to be comparable to the dolerite sills in 

 the Tertiary igneous series of Skye? It may further be 

 pointed out that the range of mineralogical composition 

 of these rocks is almost paralleled by that of the Tertiary 

 basalts themselves. Some are purely felspathic, some 

 strongly nephelinic. 



I have to thank Mr. Eustace Wilkinson for the pains he 

 has taken in supplying me with information and specimens 

 from Stewart's Brook and the Barrington Trig., and Dr. 

 Woolnough for the opportunity of examining the Warra- 

 walong material. To Mr. A. B. Walkom, b.sc, I am indebted 

 for kindly consenting to correct the proofs in my absence. 



