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CHEMICAL SCIENCE IN AUSTRALASIA. 287 
machines, and was designed by the inventors to modify 
and overcome some of the defects experienced in their practice 
with the Frue Vanner, Triumph Concentrator, and other machines 
of a like character. Their first object was to gain a larger 
cencentrating surface by widening the belt, and their second to 
do away with a needless length of belt, and thereby increase the 
facility with which the tailings could flow away. The superfluous 
length was ascertained by direct experiments with existing 
machines. With this object in view, the length of the top surface 
of the belt, from centre to centre of the two end rollers, was made 
six feet, and the width the same, thereby decreasing the length 
of the vanner belt by about one-half, and increasing the width by 
two feet, giving a large increase in the concentrating power of 
the machine, and getting rid of the tailings in about half the 
time of the Frue Vanner. Another special point in the construc- 
tion of the machine, which the inventors claim in their patent, 
has relation to the means by which the “ grade” is raised or 
lowered, and is one of which any practical man who has seen it 
will at once admit the advantage. 
The work of a machine of this class can be regulated almost 
exclusively by the alteration of the grade, without reference to 
the “uphill travel,’ and, in most machines, this alteration has 
been effected by wooden wedges, driven in or out by a hammer 
according as the grade is to be lessened or increased. As, in 
that case, the whole of the stationary framework has to be raised, 
it detracts very considerably from the stability of the machine, 
and, in the case of the Triumph Concentrator, slackens the 
driving-belt to a great extent, as the wedges have to be driven 
under the frame at the head. 
In the machine now under consideration the raising and 
lowering is done by a separate framework, made of angle iron, 
on which the supports of the shaking frame rest in suitable 
sockets. The front ends of this frame are pivoted on the main 
standing frame, which is made of cast iron, and bolted permanently 
down to the longitudinal mud-sills, and it is raised or lowered on 
the pivots by two hand wheel-screws situated at the foot of the 
machine, which work in cast iron bosses bolted to the floor. 
This machine has been built by the Mort’s Dock Engineering 
Company Limited, but has not yet been worked, pending the 
arrival of the belt ; but it may be mentioned that Mr. Egleston 
states, in his “Metallurgy of Silver, Gold and Mercury,” 
Vol. I, p. 481, that at the Silver King Mine, in Arizona, six 6ft. 
vanners were started in August, 1886, and by January, 1887, 
they had treated 10,178 tons of tails from the twelve 4ft. vanners 
on which the first concentrations were made. The average 
amount treated on each of the 6ft. vanners was twelve and a half 
tons per day, nearly twice the quantity dealt with by the 4ft. 
machine. The tails from the large vanners yielded only 2:030z. 
