Monazite and Monazite Mining 
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the magnetic field and are thrown by centrifugal force on to the 
second drum. This drum, which does not have quite so strong a 
current as the first, does not attract as many of the magnetic par- 
ticles so that some of these drop off into a second hopper, forming 
a middling product, while the stronger magnetic particles are held 
by the drum and carried a certain distance, when they get beyond 
the magnetic field and are dropped into a third hopper. On 
account of the alternate polarity of the adjacent magnets, the par- 
ticles roll over and thus facilitate the elimination of any gangue 
particles that may be mixed with the magnetic. 
Another simple drum separator is the Heberli. In this machine 
there is but one drum and the electro-magnets extend over about 
one-fourth of the area of the drum. The ore is fed to the drum 
just above the centre radius and about the middle of the magnets. 
The drum revolves in the opposite direction to which the ore is fed 
and the magnetic particles are attracted by the drum and carried 
up and over the magnets while the non-magnetic particles drop 
into the hopper below. As the magnetic particles leave the mag- 
netic field, they are dropped on the opposite side of the drum into 
another hopper. 
2. It is the magnetic separators of the second class that have 
been used principally in the separation of monazite in the Caro- 
linas. Of these machines, the Wetherill stands out most promi- 
nently and was probably the first to commercially treat weakly 
magnetic materials. The principal idea of these machines is to 
secure a very strongly magnetic field by concentrating the lines of 
force as far as possible, this being accomplished by placing the two 
poles of the magnet facing one another with a minimum air gap 
between them and by bevelling down the pole pieces to their end. 
The type of the Wetherill magnetic separator that is more gener- 
ally used is known as the Rowand type, which has a magnetic 
pole with sharp edge between the travelling feed belt and a blunt 
pole directly under it. Both of these poles are capable of being 
magnetised by an electric current which will produce a condition 
varying from weak to intensely strong magnetism. The concen- 
tration of magnetism at the sharp edge causes all the grains to 
jump to the upper pole. A cross-belt directly beneath this pole, 
which is running at right angles to the feed belt and is running 
