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Astronomy. — Prof. J. A. C. OupeMans presents as a first communi- 
cation on his journey to Réunion for observing the transit of 
Venus: “A short account of the determination of the longitude 
of St. Denis, Island of Réunion), executed in 1874.” 
In our ordinary meeting of October 30, 1875 I communicated 
a few details on the state of the computation of the observations 
at St. Denis on the transit of Venus of December 9, 1874. The 
purport substantially was, that the computations had been carried 
out as far as was possible at that moment. 
Several circumstances, independent of my will, were the cause that 
this state of things remained the same till the middle of last year, 
and that the computations could not earlier be taken in hand again. 
What I communicated then has been inserted in the Proceedings 
of that meeting. Passing by all that refers to the heliometer 
measures, which I hope to take up at some later time, I will only 
mention the fact that the necessity was pointed out of determining 
with precision the longitude of the place of observation. 
For this purpose we, viz. Mr. Ernst VAN DE SANDE BAKHUYZEN, 
Mr. Sorters and myself, have observed a number of occultations, 
not so much of the brighter stars, announced in the Nautical Alma- 
nac, as rather of fainter stars, of the 8 or 9t* magnitude, the posi- 
tions of which were not yet known with precision at that time. 
These had to be determined therefore by meridian observations; our 
honoured president readily undertook the task of having these deter- 
minations made at the observatory under his direction. 
As a rule at least four determinations have been made of each star. 
Though the added epochs show that this was done between the 
years 1879 and 1884, it lasted a considerable time, till November 
1901, before the reductions of those determinations had proceeded so 
far that the results could be communicated to me. 
At the same time my attention was called to the fact that most 
of these stars had been since also observed at other observatories. 
It thus became necessary, in my opinion, to look for all these 
determinations in the several Annals and to reduce them to the same 
epoch, (of course 1874), in order to make allowance for proper 
motion, wherever necessary. In many cases it proved sufficient to 
retain the Leiden determination unchanged. 
But besides, the errors of the lunar tables, that is to say of 
the positions published in the Nautical Almanac, had to be derived 
from observations. For this purpose the observations at the meridian- 
