( 593 ) 
6. Just as in the preceding communication the first choice of the 
opposite edges PQ and RS is arbitrary; so here too the observations 
made formerly on the multiplicity of the solutions hold good. 
c. It has been proved that the construction of the direction of 
velocity vq is possible when the vertices of the tetrahedron are imaginary. 
The cones, treated of in the first communication, having Pas vertex 
and with tangential velocities, disappear however in this case, 
their existence resting upon the reality of the vertices and the faces. 
Astronomy. Prof. H. G. VAN DE SANDE BAKHUYZEN presents, 
on behalf of the Eclipse-Committee, the „preliminary report 
of the Dutch expedition to Karang Sago (Sumatra) for the 
observation of the total Solar Eclipse of May 1901.” 
Before giving the preliminary account of our work, we shall 
recall in a few words the history of and the preparations for 
the expedition, as well in Holland as in the Dutch Indies. 
The first step towards the preparation of the expedition was taken 
on the 14% of October 1898, when, at the house of Prof. J. A.C. 
OUDEMANS and in the presence of Professors H. G. v. D. SANDE 
BAKHUYZEN and J. C. Kapreyn, Prof. A. A. NIJLAND called 
attention to the matter and at the same time intimated that already 
a considerable sum had been promised him for the purpose. 
As a consequence of this conference two meetings were held 
in the Trippenhuis on Jan. 28 and April 22 1899, which were 
attended by the same four gentlemen. ‘The plan of a Dutch eclipse 
expedition appeared to be capable of execution; a rough estimate of 
the costs was made (f 50000") and the means to get the 
necessary money were discussed. Prof. v. D. SANDE BAKHUYZEN had 
already requested Dr. J. P. v. p. Srox, Director of the Royal Magnetical 
and Meteorological Observatory at Batavia and Major J. J. A. MULLER, 
Commander of the Triangulation-brigade of the topographical service, 
also at Batavia, to provide information about the localities best 
situated for the observations and about the climatological conditions 
prevalent in these places. 
He had also addressed himself to His Excellency the Colonial 
Minister with the request to support the necessary investigations, and 
to promote the interests of the expeditions to be sent out, both 
from the Netherlands and from foreign countries. 
At the request of Mr. NijLAnp it was further decided to call in 
1) f 300 = 120 $ = 25 £ = 600 = 500 Mk, 
