„48 
It appeared immediately that the above-mentioned specimen has 
nothing to do with clay-slate, but is a genuine eruptive-rock showing 
excellent piperno-structure. The dark brownish-red faint colour of the 
chief mass seems to have given rise to Everwisy’s error. Characteristic 
are the numerous lens- or disk-shaped “Schlieren” ending in a point, 
which, being arranged more or less parallel, contrast sharply with 
the groundmass. The specimen is distinguished from the typical 
piperno by the much more intimate connection between “Schlieren” 
and groundmass, and by its inferior porosity. 
The analysis of the rock (I), for which I am indebted to Prof. 
Dr. M. Drrrricn of Heidelberg gave the following result: 
I II 
BORST Beste AL DT Sr at ee ee AGN 
TES Kn En PRE ADI LE Acree ee aed — 
PSE? NE TREE 5 
c ‘ 17,09 
tA So AN Ne Loe ey ET eR ae ae ; 
BG EEM SEL a et ae a = 
Ne TT bee NRE oe == 
OD er Ee TL TOEREN cok EEE 
Me Ore ONT ERE 
KDE EE eae BENE er DALE ee wes ENNE 9,74 
NEVO SQA REAL? SOUS ee NEN Ae EE 
BG DA SiGe eet. EA Araceae NEEN Se ee — 
. fo) re 
H°O eo eee v.38 loss of incandese. 0,94 
| over GEL kale aan Pe 
100,38 99 59 
From this analysis it appears that among all the roeks that have 
hitherto been found in the Indian Archipelago, the above-mentioned 
eruptive rock is richest in potash. From the — alas incomplete — 
analysis I] communicated at the same time’) appears further its 
Pelapis Tiang Balei granite and in the N.W. part clay-rocks 
Pelapis Genting 5 oo as aoe ie be 
Pelapis Rambai ne eN NE = 
Pelapis Tekik (Pelapis Tukang Kluwar) _,, coe ae es NWS inal a) 
Pelapis Suka 
Pulu Dua and Pulu Bulak clay-rocks. 
This does not imply, of course, that all that was called by Everwijn clay-slate, 
sh uld be classed with the rhyolitic rocks. 
1) Cart von Haver. Rhyolith aus dem Eisenbacher Thal. Verhandl. k. k. geolog. 
Reichsanst. Wien. 1868, p. 386. 
