CHAPTER Il. 
Base Measurement and Triangulation. 
Base Measurement. 
The measurement was performed on an even plain in east-west, 
close to the north of the Observatory. The plain was throughout 
nearly the whole of its length irrigated by two brooks; the bottom 
was covered with stones, in places marshy and covered with grass. 
The termini of the line were marked off by brass bolts, driven 
into the solid bed-rock. The bolts which penetrated about 6 cm into 
the rock and projected about 2 cm above it, had a cross filed into 
the surface, marking the termini ot the line. As the entire length 
of the line was nearly 1450 m, it was furthermore marked off by six 
iron plugs, adjusted into the iine by means of a theodolite. Between 
the plugs a cord was strung for guidance in the subsequent tape 
measuring. When the measuring was commenced on September 24th, 
1906, the bottom was everywhere frozen and partly covered by snow, 
and the rivers were frozen over. 
The measuring was performed by a steel tape, 24m long. Ad- 
junct to the tape were six iron plugs as well as a small, 5m long 
steel tape in a leather case. The ends of the long tape were marked 
by the plain front part of a brass cross-piece; the tape was further 
provided with rough marks for every metre, but the latter were not 
used. The small tape was divided into centimetres; besides the first 
decimetre was divided into millimetres. 
The length of the tape had been determined on the standard 
base of the General Staff in Proviantgaarden, Copenhagen, in the 
following manner: 
To the two ends of the tape a millimetre rule drawn on paper 
was pasted. One of these rules was placed arbitrarily against the 
one terminus of the standard base, after which the tape was stretched 
by an even pull, which was estimated at 5kg. The tape was sup- 
ported on the middle on a level with the line between the termini 
of the base; but the two halves of the tape were otherwise suspended 
without any support. By pulling very hard, one might increase the 
