70 



SCIENCE PROGRESS 



petrographic series may be admirably illustrated in this way, 

 as is seen in the lists given below, which are compiled from 

 tables in Iddings' Igneous Rocks, vol. ii. These series have 

 been selected from small and isolated areas, so as to ensure, 

 as far as possible, that the rocks belong to a related petro- 

 graphic series, and that there has been no admixture of rocks 

 of different ages. 



Reunion Island (Iddings, pp. 589-90) 



Phonolitic Trachyte l . 



Phonolitic Trachyte . 



Quartz-regirite-syenite 



Akerite 



Olivine -trachyandesite 



Ophitic Basalt 



Basalt . 



Essexitic Gabbro 



Gabbro 



Basalt . 



Olivine gabbro . 



Felspathic picrite 



Basalt . 



Harrisite 



r.5.1/4. 

 175.2.4. 

 (I)II.4'.i-3(4). 

 (1)11.5.2.4- 



II. 5.2.4. 



ir.5.3.4. 



11(111)5.4.4. 



(II)III.'5-3'4- 



III.5.44'. 

 III.5/4.4. 



III'.5-4(5).'5. 

 'IV.i'. 4 .i'.2. ['IV.5/4.4] 



'IV.'2/,.I'.2. ['IV.5/4.4.] 

 IV.I.,.I'.'2. [IV.5.4.3'.] 



II 



New Caledonia (Iddings, p. 652) 



Hornblende -anorthosite 



Anorthosite 



Hornblende-gabbro 



Hornblende-gabbro 



Norite . 



Ouenite 



Hornblendite 



Diallagite . 



Bronzitite . 



Phonolite . 

 Tinguaite . 

 Nepheline-syenite 



I'.5-4.5- 

 I.5/5.5. 

 II.5.4/5. 

 III.4-4'5- 



III.5/5.4'. 

 III.5.5.5. 



'IV/2.,2.2. ['IV. 5 .4.(4)5-] 

 IV.1%2.2. [IV. 5 / 4 .(4)5.] 

 'V.i. , .1.1'. ['V.5.4'4.] 



Ill 

 Tahiti (Iddings, p. 653) 



. . I'.5-i'.4. 

 . r.6.1.4. 

 . 'II/6/2.3. 



1 The use of round brackets in a symbol indicates that the magma is transi- 

 tional, and near the border line between two compartments. Thus 1(1 1.) 

 indicates a rock in Class I., but transitional to Class II. The use of dashes 

 before or after a figure indicates that the rock is intermediate between the 

 division in which it actually falls and the preceding or succeeding one. Thus 

 II.' indicates a rock in Class II., but intermediate towards III. II. (III.) would 

 indicate a rock in Class II. still closer to III. See CI. P. W.,Joum. Geo/, xx. 

 (1912), pp. 550-61. 



