B47 
It cannot be doubted therefore, that with regard to the activity of 
the lipase calcium-, barium-, magnesium- and soda salts play a part 
totally different from that of bile acids. If seems to me that from 
the above the conclusion may be drawn, that the said salts separate 
fatty acid from the solution as soap, and for that reason increase the 
fat-splitting power of the enzyme. 
Geology.—‘‘On rhyolite of the Pelapis Islands.’ By Prof. A.WicHMANN. 
The Pelapis Islands rise between the Westcoast of Borneo and the 
Karimata Islands about 1°17’. 109°10’ E. and consist, besides a 
few small islets, of the four high uninhabited and not easily 
accessible islands 1s' Pelapis Tiang Balei, also called Pelapis Hangus, 
or Pelapis Ajer Tiris, 2"4 Pelapis Rambai or Pelapis Ajer Masin, 
Bid Pelapis Genting and 4t* Pelapis Tekik *). They reach a height of 
859 m.°). Their total surface amounts to about 13 km’. 
The group of islands was visited in 1854 by the mining-engineer 
R. EveRwiJN, who communicates the following particulars about their 
geological condition. 
“In the Pelapis or Melapis Islands both neptunian and plutonic 
formations are found. The former are clay-rocks which are so much 
metamorphosed by granite and a rock analogous to syenite that it 
is often difficult to recognize its original character. In these islands 
plutonic rocks contain a small quantity of magnetic iron-ore and 
hematite *).”” 
The Mineralogical and Geological Institution at Utrecht received in 
1895 among others through the kindness of the Royal Physical Society 
(Kon. Natuurk. Vereeniging at Batavia) as a present a specimen of 
the metamorphosed clay-rocks collected by EveRwiJN *).” 
_ bh J. P. J. Barra. Overzicht der afdeeling Soekadana. Verhandel. Batav. Genoot- 
schap van K. en W. L. 2. Batavia 1897, p. 61. 
2) M. CG. van Doorn. Verslag omtrent de opname van Straat Karimata. Meded. 
betr. het Zeewezen XXIIL 2. s-Gravenhage 1882, p. 12. — Gids voor het bevaren 
van Straat Karimata. Batavia 1884, p. 31. 
3) Onderzoek naar tinerts in de landschappen Soekadana, Simpang en Matan en 
naar antimoniumerts op de Karimata-eilanden. Natuurk Tijdschr. Ned. Ind. EX. 
Batavia 1855, p. 63. Reprinted with map in the Jaarboek van het Mijnwezen 
N. O. Indië, Amsterdam 1879. I, p. 64. 
4) As Everwijn mentions nowhere (not even on the label) on which island he 
has collected the above-mentioned rock, we give here a statement of the geological 
condition of the islands according to his map: 
23* 
