5i6 



WHITMAN CROSS 



Orthoclase 



Albite 



Nephelite. 



Acmite 



Na,Si03 



Diopside - 



Olivine 



Fayalite - 



Ilmenite 



Apatite 



Etc. 



= 6.92 



29.47 1 Salic molecules, 86.74 

 51.87 [ SaL_ 



5.40 j Fern. 



4.62I 

 0.61 



^ ■ 3 y Femic molecules, 12.45 

 0.61 I 



0.76 

 0.34 



99.19 

 0.62 



99.81 



As the ratio between salic and femic molecules of this norm is 

 6.92:1, or slightly less than 7:1, the rock falls within the Dosalane 

 Class. Since the feldspars predominate over nephelite to an extreme 

 degree and there is no anorthite in the norm, the rock falls in the pcr- 

 felic order germanare, and the peralkalic rang umptekase. Soda 

 strongly dominates potash, and thus the glass belongs in the subrang 

 umptekose, but is so close to the corresponding subrang of the Persa- 

 lanes that the position is best shown by the name nordmarkose- 

 umptekose. 



The partial analysis of the trachytoid rock shows that to belong 

 also in the subrang umptekose. 



Local interest 0} the discovery. — The discovery of this lava rich in 

 alkali feldspar, so far removed petrographically from the basalts and 

 allied rocks hitherto supposed to be the only products of volcanoes 

 on the island of Hawaii, raises primarily a question of much local 

 interest. The modes of occurrence, described above, suggest that 

 there may have been quite extensive eruptions of these lavas. Unfor- 

 tunately, these rocks were found just at the close of my visit to the 

 island of Hawaii, and I was unable to search for further occurrences. 

 The terrace-like bench of Puu Anahulu is certainly a remnant of a 

 topography carved out of the trachytic rock, and it may well be that 

 beneath the basaltic flows from Mauna Kea, Mauna Loa, and 

 Mount Hualalai there is an ancient trachytic island. So far as I am 

 aware, however, no fragments of trachyte have been found in the 



