SLATE MAKING IN 1875
|Collyweston Slates from
Lincolnshire and Stonesfield Slates from Oxfordshire (Taynton Stone) are
different from most other stone slates because they are split by frost
action. In 1875 Judd provided a first-hand
account of the manufacture and use of Collyweston slate. The version of
Judd's report quoted here is from Woodward
1894 and includes some of his additional notes.
|…. the Collyweston Slates
have been dug over a considerable area, old pits being traceable from Wothorpe
near Stamford to the western side of Collyweston, a distance of more than
three miles. The valuable fissile character of the beds is merely a local
accident; and in some locations the bed of stone has been followed and
found to become non-fissile and in consequence worthless for roofing purposes.
There is only a single bed of stone (the lowest limestone of the series)
which is used for making roofing-slates. This varies greatly in thickness,
being often not more than 6 inches thick, but sometimes swelling out to
18 inches, and in rare cases to 3 feet; while, not unfrequently, the bed
is altogether absent and its place represented by sand (or sandstone).
Rounded mammillated surfaces, like the ‘pot-lids’ of Stonesfield, abound
in these beds.
|The slates are worked either
in open quarries or by drifts (locally called ‘fox-holes’) carried for
a great distance under ground, in which the men work by the light of candles.
The upper beds of rock are removed by means of blasting, but the slate-rock
itself cannot be thus worked, for though the blocks of slate-rock when
so removed appear to be quite uninjured, yet, when weathered, they are
found to be completely shivered and consequently rapidly fall into fragments.
The slate-rock is therefore entirely quarried by means of wedges and picks,
which, on account of the confined spaces in which they have to be used,
are made single sided. The quarrying of the rock is facilitated by the
very marked jointing of the beds, a set of master-joints traversing the
rocks with a strike 40 degrees W. of N. (magnetic), while another set of
joints, less pronounced, intersect the beds nearly at right angles.
|During the spring of the
year the water in the pits rises so rapidly that it is impossible to get
the slates out. The slates are usually dug during about six or eight weeks
in December and January. The blocks of stone are laid out on the grass,
preferably in a horizontal position. It is necessary that the water of
the quarry shall not evaporate before the blocks are frosted, and they
are constantly kept watered, if necessary, until as late as March. The
weather most favourable to the production of the slates is a rapid succession
of sharp frosts and thaws. If the blocks are once allowed to become dry
they lose their fissile qualities, and are said to be ‘stocked’. Such blocks
are broken up for road-metal, for which they afford a very good material.
The limestone beds above the slate-rock are burnt for lime
|After the blocks are split,
the slates are stacked on edge in circular piles or heaps [Fig 50]. Subsequently
they are shaped, and again stacked on edge according to size.
|The slates are cleaved at
any time after they are frosted [Fig 51]. Three kinds of tools are used
by the Collyweston slaters. The ‘cliving hammer,’ a heavy hammer with broad
chisel-edge for splitting up the frosted blocks. The ‘batting hammer’ or
‘dressing-hammer,’ a lighter tool for trimming the surfaces of the slates
and chipping them to the required form and size [Fig 52]. The ‘bill and
helve,’ the former consisting of an old file sharpened and inserted into
the latter in a very primitive manner. This tool is used for making the
holes in the slates [Fig 53] for the passage of the wooden pegs, by means
of which the slates are fastened to the rafters of the roof. These holes
are made by resting the slate on the batting hammer and cutting the hole
with the bill.
|The slates are sold by the
‘thousand,’ which is a stack usually containing about 700 slates of various
sizes, the larger ones being usually placed on the outside of the stack.
The slates when sold on the spot fetch from 23s. to 45s. per thousand.
Many of the Collyweston slaters accept contracts for slating, and go to
various parts of England for the purpose of executing their contracts.
|The land at Collyweston
is generally held by slaters by copyhold, the slaters paying 6s. 8d. per
pit’ to the lord of the manor (a ‘pit’ is 16 square yards) with an extra
charge of 1s. 6d. per pit to the measurer. A few workings are rented of
the lord of the manor, the slaters paying 30s. per pit with an additional
1s. 6d. for the measurer. These payments are made every year at the annual
‘slaters’ feast’ held in January.
|The manner in which the
slates are placed on the roof is as follows. The largest are laid on nearest
the wall plate, and the size of the slates is made gradually to diminish
in approaching the ridge. The ridge itself is covered by tiles of a yellowish
white tint, made at Whittlesea, and harmonising well in colour with the
slates themselves. The larger slates are, in the ordinary way, fixed to
the rafters of the roof by means of wooden pegs driven through a hole in
the upper part of each slate. But roofs are often covered with small slates
which are fixed by mortar. ….
|The slates of Collyweston
are worked with more or less vigour at the present time , although
in many new houses built in the neighbourhood of the quarries, and at Stamford,
brick and Welsh slates or red clay-tiles are employed, in place of the
freestone and Collyweston slateCollyweston Slate.
In colour the rock is a
buff and blue-hearted stone, so that some of the slates are blue, others
yellow, and many are parti-coloured. The pale coloured slates when put
up, are said to darken on exposure. The slates are usually cemented as
well as pegged on to the roofs, hence they do not fall away if cracked.
The blocks that are raised from the open quarries and galleries are of
|The slate-pits at Kirby
are now almost entirely abandoned, and they are only occasionally worked
near Dene Lodge.
|Judd J W, The Geology of
Rutland and Parts of Lincoln, Leicester, Huntingdon and Cambridge, Memoir
of the Geological Survey, London, HMSO 1875.
H B, The Jurassic Rocks of Britain Vol IV The Lower Oolitic Rocks of England
(Yorkshire excepted), Memoir of the Geological Survey, London, HMSO,