260 



SCIENCE PROGRESS 



of a series, and from one series to another. Below are the 

 figures obtained by plotting the molecular proportions (in the 

 manner already explained) of a granodiorite and of a gabbro, 

 the analyses of which are given on page 252. The increase in 



SiO? 



I. Granodiorite. 



Fig. 7. 

 II. Diorite. 



III. Gabbro. 



lime and magnesia, and the decrease in alkalies, with increasing 

 basicity, are well shown. The three figures on the opposite page 

 are plots of the molecular proportions of a diorite, a monzonite, 

 and a soda-syenite, the analyses'of which are given on pages 252, 

 253, and 256. These illustrate the variation from series to series 



