﻿240 



DR. A. HOLMES ON THE TERTIARY 



[vol. lxxii, 



desirable to have the rock analysed. With the exception of the 

 alkali determinations the analysis was made by my friend 

 Dr. H. F. Harwood (Chemical Department, Imperial College of 

 Science & Technology), and for his assistance I wish to express my 

 grateful thanks. 



Chemical Composition. 



Percentages. 



SiO, 52-27 



A1 2 0 3 17-70 



Fe,0 3 7-01 



Feb 4-48 



MgO 1-79 



CaO 5-93 



Na,0 5-95 



K,0 3-20 



K-.0 + ... 0-37 



H~0- ... 0-43 



CO., 0-51 



Ti0 o 0-56 



MnO tr. 



Total 100-20 



Molecular 

 Proportions. 



■871 



•174 



•044 



•063 



•045 



•105 



•096 



•034 



•012 

 •007 



Mineral Composition 

 (Norm). 



Orthoclase 18-90] 



Albite 37-31 I Salic 



Nepheline 6'98 [ =75-42. 



Anorthite 12-23 J 



Diopside 10-90^ 



Olivine 



0-62 



Magnetite ....... 10-21 



Tlmenite 



1-06 



Femic 

 = 23-99. 



Calcite 1'20J 



Water . 



99-41 



0-80 



Total 100-21 



Class II Dosalane. 



Ra = 2-59x10- 12 grins, per grm. Order 5 Germanare. 



Specific gravity =2 - 55. Rang 2 Monzonase. 



Subrang 4 . . . Akerose. 



A. 



B. 



C. 



D. 



SiO. 



52-27 



52-78 



51-80 



53-04 



Al o 0 3 



17-70 



19-08 



17-90 



17-34 



Fe,0 3 



7-01 



3-63 



3-10 



2-12 



Feb 



4-48 



3-79 



4-36 



6-96 



MgO 



1-79 



1-58 



3-72 



2-49 



CaO 



5-93 



5-09 



6-59 



5-86 



Na, 2 0 



5-95 



7-95 



4-74 



5-61 



K.,0 



3-20 



3-85 



3-65 



3-00 



H^O 



0-80 



0-44 



2-87 



0-37 



CO., 



0-51 



o-io 







Ti0 2 



0-56 



1-50 



1:41 



2-12 



P,0 5 



n. d. 



0-63 





0-83 



MnO 



tr. 



tr. 







Totals 



100-20 



100-75 1 



100-14 



99-74 









1 Including 0 - 33 per cent, of chlorine. 



A. Tephritic pumice, Monapo River, Mozambique (an. Harwood & Holmes). 



B. Trachydolerite, Mount Meru, British East Africa (an. Maritz). 



C. Essexite, Bekinkina, Madagascar (an. Pisani). 



D. Olivine-trachyandesite, Vellouve, Reunion (an. Boiteau). 



The most notable feature indicated by the analysis is the high 



