EL/EOLITE-SYfcNM'l'. 



181 



colleague, Dr. T. L. Walker, in the ordinary way, with the following 



results ■: — 



Chemical Analysis of Rock No. 11,460. 

 Silica ....... 556S 



Alumina ....... 23*81 



Ferric oxide (calculated as Fe 3 OJ 

 Lime ..... 



Magnesia . • 



Potash 



Soda . ... 



Graphite • • . 



Ignition • . . . 



iorg8 



The results of this analysis agree with those of the ordinary 

 elaeolite-syenites in the high percentage of alumina, very small 

 quantity of lime and magnesia and high proportion of alkalies 

 (14-39 per cent.). The silica percentage in the elaeolite-syenites 

 usually ranges between about 50 and 56 ; a slightly lower result than 

 55*68 would have been obtained in this case if the separation of the 

 titanic acid had been accomplished ; it can only be present, how- 

 ever, in very small quantities. Except for the graphite, then, the 

 Sivamalai rock shows no noteworthy divergences from the chemical 

 composition of the ordinary elaeolite-syenites. 



Loewinson-I.essing's scheme l brings out this relationship to 

 known elaeolite-syenites very clearly. 



Reducing the total to 100 and calculating the molecular ratios 

 for the oxides, we obtain for the Sivamalai rock : — 



SiO a 



A1 2 8 



Fe 2 3 



FeO 



CaO 



MgO 



K 2 



Na 9 



0*910 



0*22 

 0*02 

 0*020 *) 

 0*029 > 

 0*Ol6 ) 



0*247 



l ?1 



!Oj 



) 



O'OIO J > 



026 s; 



1 F. Loewinson-Lessing, " Studien iiber die Eruptivgesteine," C R., Vllth 

 Congres G60I. Internat., St. Petersburg, 1897, pt. 3, 194. 



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