﻿476 



DR. WHITMAN CROSS ON THE NATURAL [Allg. I9IO, 



spessartite, odhiite, etc., which, according to Rosenbusch, indicate 

 the presence of deep-seated parent magmas of the Pacific kindred. 



As to the North American continent, Iddings 1 once remarked 

 that alkali-rocks occur more abundantly along the eastern base of 

 the Kocky Mountains than in the Great Basin and along the Pacific 

 Coast. I do not know that this is the basis for Prior's 2 statement 

 that it ' has been noted that the eruptive rocks in the United States 

 become more and more rich in soda as one proceeds from west to 

 east, - ' but an examination of Washington's tables of analyses shows 

 some peculiar facts of distribution which hardly support the latter 

 generalization. 



It seems that the analysed rocks of the Pacific coast are 

 dominantly alkali-calcic and those of the eastern Rocky Mountain 

 zone more strongly alkalic. But this difference appears less striking 

 than the predominance of soda-rocks on the Pacific coast. In fact 

 there are at least a dozen rocks of the Pacific coast, from Alaska 

 to Southern California, which show a greater excess of soda over 

 potash than appears in any rock of Montana, Wyoming, Colorado, 

 or New Mexico. Conversely there are no rocks on the Pacific 

 coast so rich in potash as the leucite-rocks of Wyoming. Some 

 of these soda-rich rocks are also high in lime, but others are so 

 clearly alkalic rocks that they must be referred to the ' Atlantic 

 kindred ' of Becke. Some of the more striking occurrences are 

 indicated in the following table, with a few other rocks on which 

 comment will be made : — 



Rock. 



Xiocality, 



Analysis shows 



Norm has 



















Si0 2 . 



CaO.Na 2 0. 



K,0. 



An. 

 12-5 



Ab. 

 41-9 



Or. 

 1-7 



Ne. 

 00 



Quartz-porphyry 



Plumas Co., Cal. 



7277 



2-47 | 4-95 



0-34 



(Turner). 



















Soda-rhyolite 

 (Palaclie). 

 Aplite 



Berkeley, Cal. 



75-46 



0-95 



6-88 



1-09 



1-7 



58-2 



6-7 



o-o 



Mariposa Co., Cal. 



74-21 



1-71 



7-62 



o-io 



5-3 



63-9 



0-6 



o-o 



(Turner). 





















Soda-syenite porphyry 



Tuolumne Co., Cal. 



67-53 



0-55 



11-50 



o-io 



o-o 



95-4 



0-6 



o-o 



(Turner). 





















Soda-syenite 



Tread well Mine, 



63-01 



2-66 



io-oi 



0-39 



4-4 



83-3 



2-2 



0-6 



(Becker). 



Alaska. 



















Carmeloite 



Carmelo Bay, Cal. 



52-83 



7-35 



6-61 



2-52 



10-8 



35-6 



15-0 



11:1 



(Lawson). 





















Essexitic andesite or 



Crater of Haleakala, 



49-55 



7-01 



6-12 



2-29 j 



14-5 



34-1 



13-3 



9-4 



trachydolerite. 



Hawaii. 



















Essexite 



Salem Neck, Mass. 



4794 



7-47 ! 5-63 



2-79 



13-9 



257 



16-7 



11-9 



(Rosenbusch). 



















Augite-teschenite 



Point Sal., Cal. 



49-61 



10-05 5'62 



T04 i 



23-9 



23-1 



6-1 



13-3 



(Fairbanks). 







I 













Teschenite 



Cuyamas, Cal. 



50*55 



7-30 8-37 



2-27 ; 



11-7 



17813 



28-7 



(Fairbanks). 







i 













1 ' The Origin of Igneous Eocks ' Bull. Phil. Soc. Wash. vol. xii (1892-95) 

 p. 184. 



2 ' Contributions to the Petrology of British East Africa ' Min. Mag. vol. xiii 

 (1901-03) p. 261. 



