164 Dr. J. 8S. Hyland—Soda-NMicrocline, Kilimandscharo. 
ig) 2S take, however, only one mo- 
B wwe lecule, which course has also 
2 & Fay 2 *§ been followed in this paper. 
fo) . . 
a SO Ges Ss s = |g Considering the formula to be 
4 aa OD OD . 
< S ef@88 8 |= Ca Al, Si, O, Mr. Fletcher's 
E EAE & s = ratio would be An, Ory,.s 
= = Ab, 22 
a a on 
The triclinic nature of the 
= oc bo es E 
a De ote | Tiieepreele (7 felspar having been shown, 
SB [O|] Sis yo % © |S there remains only to add that 
BS} =! . ao ° 
p= ~ according to Brogger’s view 
=e A = the felspar should receive the 
of |e] es ah “il 1 S | | name ‘soda-microcline.” 
a | 0 a Arne : 
yi ee past eh etic a Miigge! has described the 
— occurrence of a ‘“ Natron- 
= Mikroklin” in the younger 
8 2 2 ce < «2 |= igneous rocks from the neigh- 
5 = =] . 
a x a |!& & & | bourhood of Naiwaseha Lake 
= and (i situ) from the Kiwan- 
ee ~ | & gaine Valley, two localities 
2 lel a 2. a o@ x | not far from the Kiliman- 
mR Nes) oD oom N for) Lio} “po : A 
LEE Sica Ss = dscharo massif. This felspar 
oF |e = contains “along with Na and 
S No} 29 fi ] 
Seon Er ‘ K some Ca.” Unfortunately 
Rig | 2 & no quantitative analysis is 
PC 7) 4 4 AeA 4 XS given 
DM rl Ke . 
=| = It is interesting to compare 
= = = the Kilimandscharo felspar 
= © - with others of a similar cha- 
Tal tH SS © © a o : 6 seas 
2 Sob treatin RR HE ee  Yacter from various districts. 
a|- ~ 7“ = ~ |S The following table will assist 
Sy. (es «, the comparison. 
EIS 3 The interpositions are very 
& lel & $ 228 «= |4 numerous and may be re- 
Ba 78 ea Ba Sh ede aN 5 cognized as olivine, augite- 
o . . 
ic) en s needles, apatite, particles of 
ret x the ground-mass with its con- 
na pt} at stituent minerals, and devitri- 
3 
= fied glass enclosures. The 
5 latter mostly possess a regu- 
> 0? 0g iga> 2 |, larity in their relative posi- 
a : @28: = |~ tions toeach other, and appear 
5 Dest (S| 5 . . . 
ss 8 > WeliR & : & | = imsections cut at right angles 
S yl, = : @ @ | to P and M rudely rectangu- 
me 8 £ #820 38 /+ lar. At placesgrouped round 
# oO So &®D Sac sH 5 a h f ] 
= S = 285 64/2 the vesicles in the felspar 
pT 4 | . occur very fine  acicular 
— ~~ —— 5 
.:e20 6: : o |S crystals, which are brown and 
ng 3 iS PE 0 ig & = show a decided dichroism. 
5 o'r o Sas Hom Ve ee 1N. Jahrbuch, 1886, Beilage- 
pS cao 30 “me tOe | 5 i 
OS are 2 eee St ails) Band aw spool 
pea ae a ees nc li 2 Kiwangaine lies 130 kilometres 
N.W. of Kilimandscharo. 
