October 11, 1912] 



SCIENCE 



491 



Zone 1. — Typical gabbro well -within the 

 gabbro stock. Nearly black, medium grained, 

 and with diabasie texture. (Gradation from 

 1 to 2.) 



Zone 2. — Syenitic phase of the gabbro stock 

 and within a few feet of the granite. Dark 

 gray, medium grained, and with granitoid 

 texture. (Gradation from 2 to 3.) 



Zone 3. — 1 to 3 feet wide. Biotite-schist 



allel to the main contact. (Not very sharp 

 contact between Y and 8.) 



Zone 8. — 7 feet wide. Monzonitic phase of 

 the country rock. Light gray, fairly coarse 

 grained, and not banded. (Gradation from 

 8 to 9.) 



Zone 9. — Typical (country rock) granite. 

 Pink, medium grained, and very gneissoid, 

 but with gneissic bands striking at almost 

 right angles to the main contact. 



border phase of the gabbro stock. Secondary 

 origin. (Sharp contact between 3 and 4 

 gabbro and granite.) 



Zone Jf.' — 4 inches wide. Hornblendite phase 

 of the country rock (granite). Nearly black, 

 medium grained, banded parallel to the 

 gabbro-granite contact. (Fairly sharp contact 

 between 4 and 5.) 



Zone 6. — 6 inches wide. Monzonitic phase 

 of the country rock. Yellowish gray, medium 

 to coarse grained, and banded parallel to the 

 main contact. (Not very sharp contact be- 

 tween 5 and 6.) 



Zone 6. — 15 to 18 inches wide. Chiefly 

 hornblendite phase of the granite, but with 

 numerous very narrow streaks of No. 5. 

 Nearly black, medium grained, and banded 

 parallel to the main contact. (Sharp contact 

 between 6 and 7.) 



Zone 7. — 3J feet wide. Monzonitic phase 

 of the country rock like No. 5. Yellowish 

 gray, fairly coarse grained, and banded par- 



A noteworthy feature is the fact that the 

 strike of the foliation of the very gneissoid 

 country rock is nearly at right angles to the 

 gabbro-granite contact, while the clearly de- 

 fined contact zones are parallel to the contact. 



Other features of special interest are the 

 syenitic border (except for the secondary 

 biotite-schist) of the gabbro near the contact, 

 and the almost complete absence of quartz 

 from the granite within a dozen feet of the 

 main contact. Thus the country rock (gran- 

 ite) is distinctly more basic near the contact, 

 while the gabbro is distinctly more acidic near 

 the contact. 



Whether these interesting endomorphic and 

 exomorphic changes are to be accounted for 

 on the basis of assimilation of some of the 

 country rock during the intrusion of the 

 gabbro, or on the basis of the action of vapors 

 from the intrusive, it at least appears quite 

 certain that the gabbro must have been con- 

 siderably superheated in order to have so 



