( 104 ) 



here to trace how and on \Ahat grounds this name came to be 

 general. I intend to explain this afterwards at some length. 



Finally one remark more. The nucleus of the Hondsrug in South 

 Drente is rightly said to be of a fluviatile nature. Yet it may be asked 

 whether the boulder-sand, to keep to this, immediately rests on it 

 and whether nothing can be observed there of formations known as 

 stratitied mixed and stratified glacial diluvium. This would indeed be 

 very striking and in fact this is not always the case, though I must 

 acknowledge that I have found in the discussed part of the Hondsrug 

 only with great difficulty some proliles in which somewhat acute 

 bounding lines may be observed. I must however put off this dis- 

 cussion. 1 have mentioned here only so much of my own observa- 

 tions as was strictly necessary ; in a complete treatise of it I hope 

 to have an opportunity to enter into the question of the origin of 

 the Hondsrug more in particulars. 



Groningen, Min.-Geol. Institute, June 6, 1905. 



Astronomy. — "Ajtpiv.rhnafe fommlae of a high dngree of accu- 

 racy for the ratio of the triangles in the determination of 

 an elliptic orbit from three observations H." By J. Weedek. 

 (Communicated by Prof. H. G. van de Sande Bakhuyzen). 



In connection with my paper on the same subject read on 

 22 April 1905 I now intend to derive simple approximate formulae 

 for the ratio of the triangles, which contain the 3 times of 

 observation and the heliocentric distances belonging to them, and 

 include the terms of the 5^1' oi-der with respect to the intervals 

 of time, it being easy to add. if necessary, those of the sixth order. 

 The same problem has been treated by P. Harzer, and in the 

 developments at which he arrived he attained a much higher degi-ee 

 of precision ^). Nevertheless it appears to me that his publication 

 does not render mine superfluous because of the different methods 

 of the treatment and the conciseness of my results. 



After the method, followed by Gibbs, to derive his fundamental 

 equation, we find with satisfactory approximation a general relation 

 between the values of a function F{r) at the three instants, its 

 second derivatives with regard to the time Ï^^t) at the same instants 



1) P. Harzer, Ueber die Bestimmung und Verbesserung der Bahnen von 

 Himmelskörpern nach drei Beobachtungen. Met einem Anhange unter Mithilfe 

 von F. RisTENPART luid W. Ebert bereclineter Tafeln. Leipzig 1901. Publication 

 der Stern war te Kiel XI. 



