from the Canadian Rocky Blountains. 205 



with such a definite microcline as is represented in a slice from the 

 Hungarian locality. 



The sodalite occurs in irregular patches, sometimes of considerable 

 size/ and in veins, these being sometimes very minute. It is 

 generally water-clear and in very good condition, though occasionally 

 it has a slightly dusty look or is traversed by a line of filmy 

 microliths, giving bright tints with crossed nicols, probably due to 

 incipient decomposition along minute cracks. In some parts the 

 sodalite is a mass of small, tolerably well-formed hexagons (sections 

 of dodecahedral crystals), ranging about -003" in diameter ; in others 

 they may be even -2" or -3" broad, but their outline then is less 

 distinct ; the first occasionally forming a kind of ' strait ' in the 

 second or filling little cracks in the felspars. 



Pyroxene is represented by small patches, generally few in 

 number, of a dull green, often muddy in aspect, tending, at any 

 rate towards the ends, to become acicular or to form groups of little 

 parallel prisms, an acicular microlith occasionally occurring ; the 

 clearer specimens show a faint pleochroism, the extinction angles 

 are rather small, and the mineral is a rather light green by reflected 

 light, so it is probably a soda-hornblende. It almost always occurs 

 in association with the felspars. The specific gravity of a specimen 

 with a little more pyroxene than usual is 2 '58. 



Zircon : two or three very minute enclosures may be this mineral. 

 The occurrence of nepheline is doubtful, so is apatite, and iron-oxide 

 is not present in the slices which I have examined. 



Besides these specimens of sodalite syenite Mr. "VVhymper brought 

 some fragments from other boulders in the Ice Eiver Vallej'. One of 

 these is a rather compact rock of a grey colour with a slight tinge of 

 green, in which are scattered occasional elongated crystals of felspar, 

 nearly -3" in length, and (more abundantly) similarly shaped dark 

 hornblendes, the largest being about as long ; both minerals, but 

 especially the latter, lying more or less in parallel order. Under the 

 microscope the rock is found to contain the following minerals : — 

 (1) Felspars, in fair preservation ; some apparently idiomorphio, 

 others irregular in outline, the majority ranging from •!" to '2" in 

 longer diameter, but occasionally about half-a-dozen granules less 

 than -01" are associated between the larger grains ; these mostly 

 exhibit the peculiar mottled perthitic structure common in felspar- 

 elseolite rocks, with a little plagioclase. (2) Nepheline, in character- 

 istic and good preservation ; sometimes in rather imperfect prisms, 

 sometimes interstitial between the felspars, from which I conclude 

 that the two minerals crystallized almost simultaneously. (3) 

 Hornblende : the megascopic crystals already mentioned exhibit 

 a moderately perfect crystalline outline, but are a little ragged at 

 ends and edges ; besides this they are locally fringed with inde- 

 pendent granules of the same mineral. Both are pleochroic, the 

 former changing from a rich brown to a very dark tint of the 

 same, which towards the outside is occasionally tinged with green ; 



^ I have a slice, practically all sodalite, about I inch long and rather less in breadth. 



