'WAWOKTfl-CRYSTAl.l.INK ROCKS OK NflSSOllRl. »)?,' 



Tor if the ar-iHit^*!^ and jx^rpbyvic'' arc, rrupt<v<\s tbijy n>i^hi 

 l)(' luMUNith \h" -("(.liircii) nry )v>cl<s injRuiiy ])):jcry ;iiir.l still he. 

 Ihc yi/niiiiifr. 



Till' Nvnlri ohsMs (•(]., lit ii-ia»-y loi-aj ij i(>, liincsitiiio Mini 

 -sandsUmes, and conijloiruM-Jitcs wliick had IraairK'ut.s of the 

 crystailivio ivm-Ks ^mlicddi^d in tkom, varyiRir in size? fivoiu very 

 small k) jiM)rf- Uimh two foot ip. d4ainoter. It Js the rule 

 rath'M- iliaii t ho except i<*ii ihaJ- t-ko.so frao-ni cuts arc present. 

 There viu\ tiicrofore he \w douhl wha-tcver hut that the scdi- 

 iiKMitaiy rooks are yuuii<;'-or thaw tko ujiderh'inir .12;rauit(^s and 

 porphyries. 'I'lliis ^s all the more interesthiir oh ao(\iunt of 

 'tiio o«nol nsi<i>M reached hy the Dircottn* of t!ie Arkansas State 

 '(xooloifioal Survfv. \vjf:;iclo had korotofore In'oii (•<')unt('d 

 arohccan. ' 



The porphyries and proHahly tlv liranltes of NJissouri arc 

 iintpiostioiiahly of eruptive (vriijii). Both tho field and petro- 

 ifrai>kioai evjdonoc m su[)i)ort ■eif this propositii^n lias hoen 

 irreatly inoreased sinoe June, 1SS8. 



The interestiwiT relations hetu eon tke porphyries and gran^ 

 Jtes have been .studied in detail in several looalities. At 

 present positive statements oannot he made, hut it seems 

 prohahlc that tlie granites and por|)hyries belons: to one and 

 the same eruptive mass. The ftranite areas are quite small, 

 some of then\ n^easurinir on^y a fraotion of a mile in diameter 

 while others are three or four miles. The lioundaries be- 

 tween the two ro -ks \voro \racod in ditF(>ront i)laoes, and 

 hand sp?;'iineiis caroiully taken foi petroirraphio >tud\ . All 

 the evidence <:all'.ore(J fav(\rs Hie view advaneed ai»ove. 



In the .\nuM-i(Mn ( M'n]()iii>t. \'(5l. 1. p. L>'.iO-i>:»l, the uriter 

 has fi<)furod (mmM liii eiilarijfoments of feldspar crystals in the 

 ijranito, i\nd explain<'d this secondary urowth by supposinir 

 that the o.nlar<j:(Mn"nt took place |)rior tij the final consolida- 

 tion <»f the mairnia. l*n)f. J. \V. Judd has done mo the 



J. Am. J. Science: I3). -'. • , Ilv ■■'■'■■,- 



