1520 
Part of the granites and of similar rocks of the Highlands of 
Padang may very possibly be pre-carboniferous. But the missing 
of contactphenomena in adjoining limestones cannot count as a proof 
of a pre-carboniferous age, if part of these limestones is mesozoic ; 
moreover the walls of limestone continuing sometimes uninterrupt- 
edly without transgression-conglomerates and without veins of granite 
or contactphenomena over the limit of granites and the surrounding 
sediments, may possibly be brought into contact with the granites 
by overthrusts, after the intrusion of these latter rocks; so that 
still these granites could very possibly be younger than carboniferous 
limestones resting upon them. 
As to the rocks of upper-triassie limestone, which on the isle of 
Timor give to the landscape a similar peculiar character as many 
limestones of Sumatra and the “Klippen” of the Alps and the Car- 
pathian mountains, MOLENGRAAFF *) and Wanner*) suppose them 
to be the erosion-rests of an overthrust sheet. For Djambi ToBrer *) 
has already suggested that the carboniferous rocks of Sangir-Pulau- 
Bajor, together with the mass of the Pulasian-Plepat-granites, is to 
be considered as an overthrust sheet. In the Highlands of Padang 
too there are signs which make possible a geological structure cha- 
racterised by large overthrusts; however, to bear out this supposi- 
tion we want further information concerning the age of the different 
rocks (for a good deal mesozoic and originally taken together as 
“old slates’), and concerning different facies of the carboniferous and 
these mesozoic sediments. 
Physics. — “The clustering-tendency of the molecules in the critical 
state and the extinction of light caused thereby”. By Dr. FE. 
ZERNIKE. (Communicated by Prof. Lorentz). 
(Communicated in the meeting of February 26, 1916). 
1. In a former paper by Ornstein and the author ') an improved 
formula was derived for the scattering of light by a single substance 
in the neighbourhood of the critical point. In that paper the inaccuracy 
of former approximate formulae, which gave an infinitely strong 
1) G. A. F. MoLeNGRAAFF. Overschuivingen in overschuivingsbladen op de 
eilanden Timor en Leti. Voordracht gehcuden in de Bestuursvergadering van 
18 Januari 1913. Tijdschr. Kon. Ned. Aardr. Gen. 2. XXX. p. 273. 1913. 
2) J. WANNER. Geologie von West-Timor, Geologische Rundschau Bd. IV. Heft 2. 
3) A. ToBter. Le. p..29. 
4) These Proceedings XVII, p. 793. This paper will here be indicated by 1. c. 
