GENESIS OF THE ALKALINE ROCKS M13 
cols. 2, 4, and 5 and the high magnesia of col. 2 are specially note- 
worthy. On the other hand, this hypothesis does not explain the 
dominance of potash over soda in cols. 4 and 5, nor the abundant 
water in the analcite basalt. 
TABLE III 
I 2 3 4 5 6 
S1Ohic > Gosboonooue 49.00 30.87 47.82 46.47 45-34 45.61 
ADI Ore a aes 1.30 1.50 0.67 1.33 1.30 1.96 
INA) rig ane tenet eras 15.70 13.58 13.56 15.97 16.59 14.35 
ete reese ransuocn costae 5333 6.71 4.73 5-97 5.83 6.17 
He On ate ae ania: O87 6.43 4.54 4.27 4.76 4.03 
VETO ee eee Sik 0.31 0.21 tr. 0.01 0.01 0.19 
Nig Oneness as eee 6.17 10.46 7.49 5.87 5-43 6.05 
CaO Re Re ech een 8.05 12.306 8.01 10.54 Ir.64 9.49 
IN Oa oui aioe Qa ir 3.85 4.37 1.69 2.93 plea 
110) Scpelea reece eae TG 1.87 Bo2a 4.83 4.55 3.69 
15 LAO) aay arava easier ae 1.62 2), Oy BBG 2 3D 1.12 2.60 
1B Oe ie a eee eae 0.45 0.94 1.10 0.73 0.50 0.74 
100.00 | 100.00 99.79 | 100.00 | 100.00 | 100.00 
* Includes 0.29 per cent CO:. 
Perhaps fuller statement of the hypothesis might annul some 
of the writer’s doubts which have been raised by these and other 
fundamental facts of magmatic differentiation, but at present he 
fails to see that the mechanism works as it should if the pure- 
fractionation theory were correct. 
Admission of some assimilation by magmas.—Bowen states 
(pp. 84, 89): 
As a matter of fact, plain evidence is found in the field that magmas do 
assimilate, especially when they occur in the large bodies commonly termed 
batholthss eis... It may well be, also, that some melilite rocks are formed 
by the crystallization of a syntectic magma formed by the solution of lime- 
Stones... If the absorption of any considerable amount of limestone by a 
magma can be admitted, it may be expected to have a very unusual effect upon 
themagma. 2...) . The taking of silica from feldspar molecules by the lime and 
the consequent production of feldspathoid molecules might well be supposed a 
reasonable possibility. Some alkaline rocks may, perhaps, be so generated. 
Yet Bowen believes ‘‘that normally the alkaline rocks enter into an 
eruptive sequence as the products of differentiation solely.” 
Only a very small addition of foreign lime (1 to 10 per cent) 
to a large mass of basaltic magma would be necessary to produce 
