J.F. 



Kemp — . 



Porphyrite u 



Bosses in JSTew 



Jersey. 







I. 



n. 



in. 



Si0 2 





34-61 



40-47 



31-8 



A1 2 3 





15-74 



11-86 



ls-78 



Fe 2 3 





8*52 



17-44 



15-20 



CaO 





tr. 



16-8 



14-6 



MgO 





20-03 



3-1 



3-32 



K 2 





17-14 



4-21 



5-074 



Na 2 





tr. 



1-90 



1-10 



PA 









0'95 



Loss on ignition 



2-8 



3-6 



8-1 



133 



98-84 99-38 98-924 



The sulphur was not determined ; a little is probably present 

 from the pyrite. Spec. grav. of II, 3-102, of III, 2-939. No. 

 Ill effervesced, No. II did not ; alteration therefore lowers the 

 spec, gravity. 



Many surface fragments contain scattered through them in 

 the greatest abundance pieces of shale which have become 

 involved in the eruptive mass in its passage to the surface. 

 Many fragments are little else than a kind of breccia of shale 

 held together by a cement of porphyrite. They resemble 

 nothing so closely as the fragments of rubbish that float about 

 and adhere together on any standing liquid. The shale frag- 

 ments have perfectly sharp edges and show no tendency to 

 shade by contact fusion into the porphyrite. 



Professor Emerson, in the paper on the elseolite-syenite dike 

 referred to above, describes a large bowlder in the rear of Mr. 

 Roloson's house near the syenite dike (this would be in the lower 

 right-hand corner of A2), which is doubtless a stray piece of 

 the B2 outcrop. The brief description given describes fairly 

 well the latter, and some of the original sections which were 

 studied by Professor Emerson have been kindly loaned the 

 writer. They do not differ essentially from those of the rock 

 in place, but the " square and hexagonal sections " which occur 

 so abundantly in the rock in place have been determined by 

 their high refractive power, by the absence of gelatinization 

 such as would be indicated by successful staining which failed 

 in repeated trials, and by the quite notable percentage of P 2 B 

 in the second analysis above, to be apatite instead of nepheline. 

 Its abundance, however, is, as stated above, one of the most 

 remarkable features of the rock. 



These masses have been described as bosses or knobs rather 

 than dikes under which name the New Jersey report designates 

 them because the large hill in B2 is nearly as broad as long 

 and the other exposures resemble low knobs or blisters. It is 

 possible that the mass of these hills under the soil may be 

 baked shale with a backbone of eruptive rock in the form of a 



