based on ammonium perchlorate, of Swedish make, named territe has come
into use alongside of gelatine dynamite.
Concerning the general effect of blasting in the Swedish ore mines the
amount of rock broken down varies on an average between 8 and 15 tons,
and, where circumstances are favourable, 20 to 25 tons per kilogram of
explosive, and between 2 and 3 up to 8 to 15 tons, and in the open-cuts in
the export fields between 1 0 and 2 0 tons per meter drilled.
Swedish Hammer-drill Machine.
Mining Methods. The oldest method of mining employed in Swedish
ore mines is “pallbrytning” (underhand stoping) this ancient method is still
extentively employed. It is used principally in open-cut mines; for underground
mines nowadays it is chiefly the smaller mines that stick to it;
the bigger mines are going over to other methods.
The underhand stoping method was down to 1858 the only method of
mining employed in Swedish ore mines; in that year takbrytning med
igensattning (overhead stoping with filling) was introduced in the Amme-
berg zinc mines, but it was not till 1869 that the method began to be employed
in a Swedish iron mine, notably at Dalkarlsberg, after which the
method was gradually introduced into quite a number of mines, both in
Central Sweden and in the Gallivare Malmberg in Norrbotten. About
1900 a new mining method was introduced, namely magasineringsbrytning,
(shrinkage stoping) that is overhead stoping without filling, in which a
considerable part of the ore broken is allowed to remain until the working
room has been excavated. This method, which was first adapted at Gran-
Ore Bins,¿Dalkarlsberg.
gesberg and Striberg, has gradually obtained a very general application,
and in many places has replaced the overhead stoping with filling process
or the underhand stoping method. The crosscut slicing with filling (tvar-
brytning med igensattning) has been employed since the seventies in a
number of mines with loose or readily crumbling ore; in the last ten years,
however, the methods employed in mines of this kind have been the subdrift
of caving system (rasbrytning) specially the top slice system.
In the Swedish coal mines is as a rule used a combination of pillar and
stoll working and longwall system.
The shafts in Swedish mines are either perpendicular, which is usually
the rule, or inclined following the dip of the ore body.