44 KOÏÔ : NOTES ox THE GEOLOGY 



aualcime seems, so far as my experience goes, to be exclusively 

 confined to this type, though it is possible that the colourless 

 base in minute interspaces of other Basalts of the Hoko Group, 

 might turn out to be that mineral, if the means are at hand in 

 ascertaining its presence. 



Another accessory to Ije mentioned is apatite in colourless 

 prisms, which is especially plentiful in this type. 



The colourless base and analcime are rather unexpected 

 guests ill the basic, black roch, such as we have here, and the 

 mode of occurrence is that they fill up the polygonal interspaces 

 left by the crystals of other components of the rock. If we 

 accept the primary origin of the analcime, as Pirsson^^ would do, 

 it is all the more very striking to see that the residuum of 

 a Basaltic magma should have an exact composition of 

 Na20*Al203'4 Si02'2HoO. Yet the analcime seems to all appear- 

 ances to be of primary origin, if we take into account the 

 perfectly fresh state of the rock in which it is found, and not 

 only in the Basalts of the Hoko Group, but in the Teschenite 

 of the Nemuro promontory in Hokkaido, I had several occasions 

 to observe the same mode of occurrence of the aualcime, so that 

 it could not be attributable to a mere accidental circumstance 

 to find it in such state, as several foreign writers also noticed 

 the same. It excludes the idea of its having replaced the base 

 which formerly occupied the place of the now-existing analcime. 



The present mode of occurrence of the analcime may perhaps 

 be explained by supposing that, when the Basalt luas consolidating 

 0)1 the i^uiface in a quiet state, carrying in it the intratelluric oli- 

 vine, the 7iewly created crystals, such as those of plagioclase, augite, 



1) ' The Moncliiquite or Analcite Group of Igneous Eocks.' Journ. Geol., Vol. IV., 1896, 

 p. 679. 



