CHEMICAL RELATIONS OF A PETROGRAPHIC PROVINCE 691 



the reservoir extension on the slope of Mt. Royal. A curve was 



obtained in a similar manner for each of the 36 analyses of the series. 



These curves were then combined so as to give a value to the 



third dimension. For this purpose each curve was traced on a 



camptonite: 



RESE^RVOIFt EXTENSION - MONTffE/iL. . 



sTb^ 



T,0^ M.^O^ Fe^Oj FeO 



M9O 



Fig. I 



thin rectangular sheet of metal, which was then cut so that its 

 upper edge presented the outline of the curve, while the other 

 three edges retained their rectilinear character. The form of the 

 sheet representing the analysis of the camptonite has thus exactly 

 the form of the diagram shown in Fig. i. 



