86 SEFSTROM ON THE FURROWS WHICH TRAVERSE 
as to the direction of the furrows on a small scale, as on this 
and similar rocks, I have seen verified when I have examined 
the rocks on a large scale, or mountains. 
In order to explain this, whilst exercising the students of the 
mining-school, I measured a considerable tract here around Fah- 
lun, and, with the assistance of the mining and other maps, I 
constructed a map*, on which, by actual levelling, the lines are 
placed as on the ground, corresponding to every tenth foot above 
the surface of the water of lake Runn. These lines, placed here 
with the same design as those on the sketch of the rock in 
Pl. III., give, without any transverse section, a sufficient idea 
of the configuration of the surface of the earth on the place in 
question ; and, in order to see how this slope lies with regard to 
those nearest surrounding, the heights were inserted by Mr. H. 
Wegelin, who has studied the tract around here, and determined 
them according to the ordinary method of surveying. 
The first thing that I did was to see if the compass was at- 
tracted by any ores in this district. For this purpose I tried the 
direction of the needle on many places on the measured and 
marked base-sectional lines, after the following method,—viz. that 
the sight line of the telescope was taken in the direction of the 
base line, and the observation made on the needle, to see if it 
everywhere, on the same line, pointed to the same degree. At 
the point of intersection of the lines the observations were com- 
bined, by which I not unfrequently found that the compass, in 
the neighbourhood of the copper-mines, was affected by the 
magnetical pyrites contained in the ore; but as this, however, 
never made the difference of half a degree on the needle which I 
used, I have not made any remark on itt. 
The hill at this place, which presented the best situation for 
making investigations with the view in question, is just that 
on the northern end of which the mines are situated, between 
Fahlu-a (rivulet) on the eastern side and the lakes of Onsbacks- 
dammen, and Wallen on the western. This hill has three tops, 
which are very plainly furrowed :—Grufrisbergstoppen furthest 
to the west, Pilbobergstoppen in the middle, und Galbergstoppen 
further easterly. On every side of this hill slopes are found 
with somewhat distinct furrows, with exceptions on the southern 
side near the top, where, however, some indistinct slopes are 
met with, otherwise the rock in situ is covered on this side with 
* [This map is Plate vii. in the Vetenskaps-Acad. Handlingar.—Eb. ] 
+ In mining researches, such, however, would demand attention. 
