461 
minimum in India and Australia and weakened by the maximum, 
as must undoubtedly be the case, the successive stages may be ima- 
gined as follows. During the barometric minimum an_ increased 
mixing takes place with the cool air from higher latitude together 
with an increased supply of cold water. By these causes after the 
barometric minimum a temperature minimum is developed in the 
lower strata of the atmosphere. In the upper strata, however, by 
the greater heat of condensation, resulting from the increased ascend- 
ing motion of the air, a temperature maximum will develop simul- 
taneously with the barometric minimum and this maximum will in 
its turn determine and strengthen the barometric minimum. This 
latter process will continue until the progressive sinking of the tem- 
perature of the water and the air below, cause the condensation to 
diminish and the atmospheric pressure to rise by a smaller supply 
of water-vapour and greater density of the air and in this way the 
following phase is prepared. 
The energy required for keeping up this process is partly supplied 
by the increased heat of condensation during the barometric minimum 
and may for another part be derived from the interaction with the 
active centres of higher latitude where the deviations, once started, 
reinforce themselves, contrary to the tropical system of circulation 
where they are self-regulating *). 
Weltevreden, May 10, 1912. 
Geology. — “On Orbitoids of Sumba”. By Dr. L. Rurren. (Com- 
municated by Prof. A. WicHMANDn). 
(Communicated of the meeting of September 28, 1912). 
From Professor Wichmann I received a short time ago a small 
collection of specimens of rocks and fossils belonging to a collection 
gathered by Mr. H. Wirxamp, geologist of the Bataafsche Petroleum- 
Maatschappy in the southern part of the Island of Sumba. 
I beg to communicate here some particulars about the Orbitoids 
found in this collection. In 5 of the samples sent to me I discovered 
Orbitoids i.e. in 4 numbers (81, 114, 166 and 167) the subgenus 
Orthophragmina, and in 1 number (105) the subgenus Lepidoeyclina. 
1) Cf. Metereol. Zeitschr. loc, cit. 
