354 ^/''' AmcricMi Geologist. Juno. i89<.» 
from liparytes. The phonolytes and the eleolitic syenites are 
identical ; the diminution of RO and R=0 in the phonolytes and 
the increase of R^O^ is explained perhaps by the metamorphism 
of the eleolitic syenites. There are also similar relations be- 
tween the leucitic basalts and the nephelinic. Aside from 
those four groups it is found that the alkalies and the alkaline 
earths are antagonistic, and the differences of their respective 
quantities in the rocks can be used to characterize the chemical 
types of the magmas. 
3. The variation of the sum (R^O+RO) depends on RO, 
except in one small portion between the andesytes and the sye- 
nites-the zigzags of two lines viz.: of RO and of (R=0+RO) 
are turned in the same direction. 
4. The line of R^Os follows the line R2O (except the four 
parts mentioned above, viz.: leucitic and nephelinic basalts, 
diorytes, melaphyrs, etc.) On the contrary the zigzags of RiOa 
and of RO are turned in opposite directions (except for the 
acid rocks and the orthophyrs. andesyte and syenite). There- 
fore when the magma is separated into two the oxides R-O^^ 
(and notablv AbOa) follow the alkalies and are antagonistic 
against the alkaline earths. 
5. From what precedes it results that R=03 and(R,,0+RO) 
are antagonistic except in the acid rocks and the portion of or- 
thophyrs, andesytes. 
Conclusions draiL'H from the Qirvcs I of Table II. 
(i) The variations in the quantities of NaaO and K^O are in 
the same direction, except in the granites, quartz porphyries, 
liparytes, andesytes, syenites and dacytes, and the ultra basic 
rocks with leucite and nepheline. 
(2) K2O is antagonistic with CaO and MgO ; — therefore in 
(lififerentiation K2O shares in a different "noyau" (Rosenbusch) 
from CaO and MgO. 
(3) NasO also is antagonistic against CaO and MgO, ex- 
cept in the acid rocks; as to CaO there are also two or three 
exceptions. 
(4) AbO^ is antagonistic against CaO except in the ultra 
basic rocks ; in the same way it is antagonistic with MgO most 
frequently. 
(5) The variations of the quantities of CaO and MgO are 
