In message <001801c3b296$6564f6e0$58c1fea9@mikegill>, Mike Gill
<[log in to unmask]> writes
>Firstly, edge rollers only seem to have had a very limited application
>for crushing lead ore.

Except, of course, in Derbyshire; or, in fact, the northern half of the
Peak District. John Barnatt will shortly publish an article which lists
some 40ish horse grinder circles in the northern Peak District. For some
obscure reason these only seem to occur north of the River Wye in any
quantity - in fact he claims that he only knows of one horse crushing
circle on a mine site outside Derbyshire, and this was for crushing
anthracite at a coal mine in mid-Ireland!!!!

It has to be said these horse grinders can largely be dated to the 19th
century, long after the mines were in their heydays. I suspect that
their use was for reworking tips for Belland Ore and the large quantity
of tip material required mechanisation, but why someone saw fit to
either invent or import the concept of horse grinders we don't know.
Possibly someone had been to Mexico or somewhere similar and saw horses
being used on silver ores - who knows.

>Stamps were even less likely to feature, though they were used for
>crushing glassy slags.  Stamps were sometimes used alongside roller
>crushers for crushing the chats returned from the hotching tubs.
>

>Secondly, Peter is right, the importance of a uniform sized feed for
>the efficient opperation of each stage in the dressing process cannot
>be overstressed.
>
>The dressing process and its mechanisation has interested me for a long
>time - being one of the few areas of non-ferrous metal mining to see
>the sustained introduction of major, inter-related innovations.  I long
>since concluded that there is no easy answer to the point made by Peter >C.
>
>Pre-19th century mine owners obviously saw brangled veins as a
>potential source of ore, but were constrained by the cost of mining and
>dressing each bing (in other words the 'unit cost').  Many factors must
>have contributed to create a demand for mechanised dressing (not just
>crushing) and to make it possible for it to succeed.  These factors
>include (in no particular order):-
>
>Organisational changes which allowed for the consolidation of smaller
>mines into better capitalised ventures, covering bigger areas.  This
>process varied by area.  In the North Pennines, for example, large
>companies (London Lead Co. and the W.B. Mines) were active from the
>late C17th.  In other parts of the country, small mines predominated
>until much later.

Once again Derbyshire is somewhat different. Large scale organisation
was earlier and it was later that the orefield deteriorated into smaller
scratchings. The London Lead Co. had departed by 1764, the Yatestoop
Mine collection of Newcomen Engines had finished by 1740 and Deep Rake
on Longstone Edge was reduced to be reworked by 1730. Virtually all the
19th century attempts to mechanise mining were dismal failures, viz.
John Taylor. Only Wass working a completely new area at New Millclose
was a success

>Even where mines covered large areas, it is not always clear that they
>were organised (or even perceived) as anything other than a group of
>small workings.
>
>The introduction/wider use of railways in the later 18th century
>allowed more vein-stuff to be moved underground more cheaply/easily.
>
>Greater centralisation of these larger mines - made possible by horse
>levels, whim shafts, railways etc.
>
>A more systematic approach to prospecting for, developing and working
>new veins.  Particularly changes in the way miners worked.  Mechanised
>dressing allowed them to remove larger parts of the vein as opposed to
>picking out the richest parts.
>
>A general reduction in the 'real' price of lead (not sure about copper,
>tin etc) over time.  Hence an increasing need to maximise the
>percentage of ore recovered.
>
>Mike

--
David Williams