( 483 ) 
The micrometer screws, the levels and the differences in diameter 
of the pivots were accurately investigated and all irregularities were 
accounted for. For the illumination, electric lamps were always used, 
for which the current was supplied by accumulators. 
The latitudes were determined by zenith distances of northern and 
of southern stars. For the northern stars only the two pole stars, 
a and d Ursae Minoris were used; the southern stars were chosen 
so that they had a northern declination from 6 to 14°, and conse- 
quently culminated at zenith distances almost equal to that of the 
pole, i.e. equal to the co-latitude. 
As a rule, for each determination 16 zenith distances of the pole 
stars were observed, without regard to the point on the parallel 
they occupied; of the southern stars, four in number, 8 zenith dis- 
tances were observed, four before and four after culmination ; so 
that each complete determination of latitude rests on 32 zenith 
distances north and 32 south of the zenith. 
At each station four such determinations were made in four 
positions of the circle which differed by 45 degrees. If we bear 
in mind that the reading was always made by two opposite 
microscopes, the zenith distance of each star may be said to be 
determined by eight different ares of the circle, hence the periodic 
error of the graduation may be considered as almost entirely elimi- 
nated. 
The declinations of the stars used were taken from the Berliner 
Jahrbuch, while due account was taken of the latest corrections, 
published by Auwers in nos. 3927 -29 of the Astronomische Nach- 
richten. Finally the latitudes found were corrected for the polar 
motion, according to the latest data furnished by ALBruEcHT. 
For the azimuth determinations only the Polar star was used at 
different points of its parallel. The horizontal distance between the Polar 
star and the object was measured four times in 12 positions of the 
circle, differing 15 degrees; this was done aceording to the follow- 
ing scheme : 
Object, Polar star, Polar star, Object, reverse the instrument 180°; 
Object, Polar star, Polar star, Object, while for each pointing at 
the Polar star the level was read in two positions. Accordingly 
each determination of azimuth consisted generally of 12 series of 8 
observations i.e. 2 complete determinations each ; hence of 24 complete 
determinations. 
As object was used either a lamp, or a heliotrope, in most cases 
a heliotrope. Its position with relation to the adopted centrum of 
the station was determined by the Triangulation Service. 
