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Development Mining
In total there were 76 development headings, (drives,
winzes, raises) amounting to 1,835 metres advanced during the life of the Cost
Book.
We do not know the cross sectional size of
these tunnels, but for the drives we could expect the height in the centre to be
barely that of an average man and the width just wide enough for a trammer to
work, while the winzes and raises might be 1.5 metres in diameter or less.
Raises
There are only four locations
recorded in the Cost Book showing rising, i.e. driving a tunnel upwards.
This is understandable when one considers the effort required for hand boring
up-holes, but it is interesting to note that one raise was driven by 4 men in
Dobree's lode for 23.78 metres giving an average advance of 7.93 metres per
month which is a better performance than most of the drives and winzes.
The cost worked out at £2.14 per metre.
Winzes
Winzes are sunk to connect the
main levels within the lodes in preparation for the production, or stoping of
the ore. The main levels from New Engine Shaft in Wheal Agar during the life
of the Cost Book were at Adit 36, 48, 60 and 70 fathoms from surface, and from Windstraw Shaft at Adit 33, 40, 50, and 60 fathoms. Winzes also assist
ventilation through the mine.
The average advance per month
for sinking winzes was 4.3 metres with costs varying from £2.50 to £4.00 per
metre.
Drives
Drives are tunnels driven
along the strike of the lode and act as the main 'roads' for access
to the stopes and conveying the ore to the shafts. There are 47 locations
mentioned in the Cost Book.
The following are some
examples:-
Driving the Shallow Adit south
(Druid Adit)
-
Total advance 57.93 metres,
averaging 5.79 metres per month
-
2 men in pare. Net pay
to pare for 10 months £52.00
-
Cost per metre including
materials £1.03
Drive west from Windstraw
shaft on 40 fathom level
-
Total advance 62.93 metres,
averaging 5.24 metres per month
-
4 men in pare. Net pay
to pare for 12 months £149.80
-
Cost per metre including
materials £3.16
Drive west from Boundary Shaft
on 40 fathom level
-
Total advance 45.91 metres,
averaging 6.56 metres per month
-
4 & 6 men in pare. Net
pay to pare for 7 months £87.44
-
Cost per metre including
materials £2.66
Drive east from Windstraw
shaft on 50 fathom level
-
Total advance 71.27 metres,
averaging 6.48 metres per month
-
4 & 6 men in pare. Net
pay to pare for 12 months £188.98
-
Cost per metre including
materials £3.69
Drive west on North lode 50
fathom level
-
Total advance 82.22 metres,
averaging 5.14 metres per month
-
6 men in pare. Net pay to pare
for 16 months £255.12
-
Cost per metre including
materials£5.14
Drive west from New Engine
shaft on 60 fathom level
-
Total advance 106.12 metres,
averaging 5.31 metres per month
-
4 & 6 men in pare. Net
pay to pare for 20 months £270.83
-
Cost per metre including
materials £3.32
Drive west from New Engine
shaft on 70 fathom level
-
Total Advance 47.53 metres,
averaging 4.32 metres per month
-
4 & 6 men in pare. Net
pay to pare for 11 months £139.80
-
Cost per metre including
materials £3.83
Driving Cross-cut north on the
60 fathom level
A cross-cut is a tunnel driven
at right angles to the strike of the lode and is therefore usually in harder
waste rock
-
Total advance 22.21 metres,
averaging 3.70 metres per month
-
4 men in pare. Net pay
to pare for 6 months £62.00
-
Cost per metre including
materials £3.90
Driving south on the the
70 fathom level crosscourse
A crosscourse is a fissure,
with or without any metalic content, cutting across the usual direction of the
main lodes. At Wheal Agar it is clear that the particular crosscourse contained
some soft material to make driving less difficult.
-
Total advance 59.19 metres,
averaging 8.46 metres per month
-
2 & 6 men in pare. Net
pay to pare for 7 months £75.21
-
Cost per metre including
materials £ 1.66
The above are but a few of the
work locations underground but they can be considered as being representative of
the whole. It is interesting to note that 25% of the 76 development
headings were only worked for one month or less, which may be indicative of
differing opinions regarding the best mine planning.
Ventilation must have been bad
especially in the new areas of the mine before connections were made to other
workings. In the Cost Book there are only a few references to ventilation
and air sollars.The clearest is in December 1858 when the 4 man pare of Francis
Cocking & Co. were driving the 60 fathom level east on south lode and the entry
states 'putting in air sollars 26 fathoms at 8d' (pence), which amounted
to an extra £0.87 in their pay.
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