322 Scientific Intelligence. 
Another line of shocks is shown to have the direction from Mt. 
Vultur southwest through Potenza to Papasidero. 
rom the facts presented, Professor Suess shows that there is a 
close connection between the volcanoes and the earthquakes. He 
clu 
phenomena mete from fractures that have been ig nine ed 
through other ae 
ie Distinctive optical properties of the Feldspars. pl FOS 
Ux has recently inv sted Sata ane optical properties of the tri- 
An feldspars (C. xxx, Feb, 8, 1875). The principal results 
obtained by him are contained in the following table, in which 
Bz stands for bisectrix. 
ALBITE. {OLIGOCLASE.|LABRADORITE|/ ANORTHITE 
Acute bisectrix always + ‘generally —| always + ways — 
sometimes + Position of 
Angle made by the + Bx. witha e Bx. 
normal to i-% (g) 15° 18° 10” 30° 40’ has no 
Same, with a normal to O(p) 18° 35’ 68° 56° simple rela- 
Angle e by the line in which Line parallel i 
the plane of the optic-axes cuts ge planes ob 
4-7, with ae i-% | O(g’| p) 20° 0 |e-%. 27°-28° | served on 
Same, with edge 7-%|J(g’|m) 96° 28(front)) “  “  |37°25/-36°25' ithe cryst’ls. 
Ordinary dispersion v(+ Bx.) | p<co( p<u( -Bx 
p< o( + Bx.) | p>v(+ Bx). 
Dispersion parallel or perpendic-| Inclined; | Crossed; also| Crossed; also, Incl 
ular to plane of polarization probably also’ slight in- | slight in- 
slight clined. 1 
a8 nt reais angle (in air)| 
or red ra 80° 397 89° 357 88° 15’ | 84° 58’ 
er blue sll 81° 59’ 88° 31 87° 48’ | 85° 59” 
(Roe tourné) ——_ (Labrador) | (Somma) 
edestrand) 
e axial ete Sn is quite constant for albite, labradorite 
and eis but varies for oligoclase even in different sections 
taken from the same sapere: DesCloizeaux concludes from his 
hit 
contrary to the views presented by Tschermak. Andesite he con- 
elu ae si, be altered oligoclase, while tschermakite is bsp 
wit - 8. 
