338 REPORTS ON THE STATE OF SCIENCE. 
ancient times up to the end of the nineteenth century about 60 M.T. of 
iron ore were mined. When comparing this quantity with the amount 
of ‘ore expectant’ still left in the mines, one arrives at the result that 
the remaining part may be estimated at most at 40 M.T. This corre- 
sponds with an additional sinking of the average level of all the mines 
150--200 m., which is the greatest depth one can reckon upon in such a 
case. 
A few words may here be said about the persistence of the Swedish 
ore deposits in depth. Since the mining of these ores has been carried 
on for centuries, we have a lot of experience on this question. In most 
cases the workable ore of a single deposit does not extend to a depth of 
100 metres : this represents the great bulk of all the iron mines. Among 
the others only a few continue to depths between 100 and 200 metres, 
and the cases in which the ore could be followed to depths over 
200 metres are easily counted. Only one mine has exceeded a vertical 
depth of 400 metres or reckoned along the pitch 500 metres. 
It is not easy to give a geological explanation of this fact, but 
experience on this point speaks very clearly. 
If we add 9 M.T. for ore reserves in old mines already abandoned 
but which possibly may to some extent be worked again, and for new 
finds, we arrive at an ore quantity in Central Sweden of— 
M.T, 
Grangesberg . - : : : : : : : ep 
Other mines . F A ; 3 3 : 4 . 40 
Old abandoned mines and new finds : ; f s : 9 
100 
2. Ore Province of Norrbotten. 
In this ore province the ores were not worked to a noteworthy extent 
before the end of last century. In consequence thereof we have very 
little experience about the depths to which the deposits reach ; also the 
mode of formation of the ores is doubtful. These circumstances make 
great caution necessary when attempting to estimate the ore supply, and 
it cannot be calculated at great and uncertain depths. 
The most remarkable of the ore deposits of Norrbotten is Kiurunna- 
vaara. The deposit here forms a mountain ridge, rising to a height of 
250 metres above the level of Lake Luossajirvi. It crops out for a 
length of 2:8 kilometres, with a width ranging up to 200 metres. The 
area of the outcrop is, according to the calculation of Professor W. 
Petersson, 286,000 square metres. 
On account of its occupying the higher parts of a mountain ridge, the 
deposit is to a certain degree ‘developed’ by Nature. Several diamond 
drillings and a gallery have served to develop this part of the deposit still 
more, so that it may be considered as comparatively well known. Already 
Lundbohm, in the year 1897, estimated the ore supply above the level 
of the lake to be 215 M.T. This estimate was confirmed through the 
calculation made by Professor Petersson in 1907, who came to a figure of 
about 200 M.T. above the lake. In both these calculations it is reckoned 
with 4:5 tons of ore from the mined work, which I consider rather high, 
taking into consideration that this extremcly pure ore also contains some 
parts of barren rock. Although I should prefer the figure 4 tons of 
