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February, 1943

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Until nearly the end of the nineteenth century commercial alum was obtained from the alum shales which form part of the Upper Lias of the Jurassic System of North-East Yorkshire. During the height of their prosperity the quarries made considerable profits and there was much competition; and this competition, combined with the increasing use of Spence's process elsewhere, caused many of the works (a "works" comprising a quarry and an extraction plant) to be closed as the market was becoming overstocked with alum. About 1860 Peter Spence patented a method for obtaining alum more cheaply by treating certain shales of the Coal Measures with sulphuric acid, and established plants at Manchester and Goole.

Alum is now manufactured from blast-furnace slags, bauxites and other hydrated forms of alumina, clays and other alumino-silicates There are still, however, vast reserves of alum shale in Yorkshire in which potash alum occurs as an efflorescence, and these notes are written not only as a brief description of a dead industry but also in view of their possible strategic importance. Alum has many uses in industry apart from its medicinal and astringent properties; it is used as a fireproofing agent, as a mordant in dyeing, as a size in paper manufacture and in the dressing of leather.

Early history

Prior to the middle of the fifteenth century the supply of alum came from Turkey and a flourishing trade was done between Asia Minor and Italy. The Italians required the alum for their dyeing establishments, and after the capture of Constantinople by the Turks in 1453 they objected to buying it from Islam and sought other sources of supply. John di Castro, who had been a dyer of cloth in Constantinople and had watched the manufacture of alum, was driven back to Italy. There, at Tolfa, he discovered an alum rock and was duly rewarded by the Pope, who thereupon began the great papal monopoly in alum; an industry thus began at Tolfa which still exists, and is the source of the commercial Roman alum.

The Pope had no difficulty in keeping up his monopoly, and excommunicated any who dared to compete. He advanced the price of his alum gradually until, as Hoover¹ remarks, "the consumers had greater complaint than against the Turks."

Introduction into Britain

Although German miners had settled in England long before the reign of Queen Elizabeth, the queen did much to encourage home industries and in order to escape the payment of tribute to the Pope she invited to Britain "certain foreign chymistes and mineral masters." Among them was one Cornelius Devoz, to whom was granted the privilege of "mining and digging in our realm of England for allom and copperas." After that there is a gap in our knowledge of the alum industry, but the Belham Bank works near Guisborough are supposed to have been opened in 1595. According to A. Anderson² the first alum works in England were erected at Guisborough in 1608. The person responsible was either Sir Thomas Chaloner, who according to T. Pennant³ suspected the presence of alum because the trees in the district were of a weak colour, and according to G. Young⁴ because of the taste of the water issuing from the shales; or Sir J. Bouchier, who is said to have improved upon the method of manufacture. At any rate, Chaloner apparently induced Italians to leave the papal works at Tolfa and come to Yorkshire, for which he was excommunicated and heavily cursed by the Roman Church.

The Pope's price of alum had reached the equivalent of £53 per ton, but upon its introduction into England the price fell to £20. The manufacture was carried on at a loss until the union of England and Scotland, when a British monopoly was created and the Yorkshire works amalgamated into a royal mine, which was leased to Sir Paul Pinder at a rental of £15,000 per annum. He employed about 800 persons and was enabled by the royal monopoly to keep the price up to £26 per ton. The monopoly ceased at the end of the reign of Charles I, when the manufacture increased so much that the market became overstocked and in 1736 the price of alum fell to £10. The price thereafter varied considerably, and during the most prolific period the output was 5,000 to 6,000 tons per year.

Growth of the industry

Jet also occurs in the Upper Lias in the Jet Beds, and was probably mined at and around Whitby from very early times, as ornaments have been found in Celtic barrows and Roman coffins. It was mentioned by Caedmon in the seventh century and in the rolls of Whitby Abbey in the fourteenth, and from the reign of Elizabeth the working of jet was carried on industriously. In spite of this, however, Whitby remained only a small fishing village until the introduction of Chaloner's (or Bouchier's) manufacture of alum from the alum shales, when the village extended itself into a town. As coal became necessary in the extraction process, ships were first sent to the Tyne for coal about 1650, after which ships were built at Whitby and the town became a port of some small importance.

The following works were in operation at one time or another between late in the sixteenth century until the latter half of the nineteenth century, and where possible the dates of working are given: Belham Bank, near Guisborough, 1595-1620, 1766-1800; Spa Wood and Rock Hole, near Guisborough, 1600-c. 1615; Sandsend, 1615-c. 1885; Boulby, closed since 1861 ; Lingberry, Lofthouse (or Loftus), closed since 1863; Peak, near Robin Hood's Bay, closed since 1817; Saltwick, near Whitby, 1649-1708, 1755-1791 ; Little Beck, 1660-1809; Carlton, 1680-1774; Holmes, near Sandsend, opened 1680; Hagg, near Saltburn, 1680-1720, 1765-1776; Kettleness, 1728-c. 1736, 1742-1754, 1767-c. 1861 ; Osmotherley, 1752-1772; Stoupe Brow, near Robin Hood's Bay, 1752-c. 1817; Eskdale Side, 1764-c. 1817; Godeland Banks, 1765-1805; Ayton, 1765-1771 ; Kirkby; Ash Holme, near Sandsend; Rock Hole, near Sandsend; and Old Peak, near Robin Hood's Bay.

These works, the localities of most of which are shown on the accompanying geological map, are situated on the cliffs of the seashore, among the great escarpments inland, or in stream-cut gorges-anywhere, in fact, where the alum shale could be removed with a minimum of overburden and where the waste rock could be disposed of with little difficulty.

General geology

The Jurassic System, which is exposed well in North-East Yorkshire, consists of a remarkable series of strata which are famous as having first led William Smith, in 1799, to the theory that beds could be identified and correlated by their fossils, and of late years correlation has been carried out more in the Jurassic than in any other system, with the possible exception of the Coal Measures of the Carboniferous. Smith first visited this region in 1794 as a surveyor and noticed the geological resemblance between the Hambleton Hills and the Cotswolds. But it was not until 1821 that he published his large geological map of Yorkshire ; this map has since been shown to be fairly accurate, but Smith confused the Alum Shale with the Oxford Clay.

The next important work in this region was published in 1829 by J. Phillips,⁵ who was to publish another geological map of Yorkshire in 1853, an improvement on Smith's. After this, publications of varying merit appeared on the Yorkshire Jurassic System, including the Alum Shales of the Upper Lias, but C. Fox-Strangways admirably summed up our knowledge in a Memoir of the Geological Survey,⁶ which is a standard work on the subject. At the outbreak of the war, work had begun on the British Regional Geology handbook dealing with East Yorkshire, but was not completed.

The general shape of the Jurassic outcrop in Yorkshire is roughly circular, over an area of about 1,000 square miles. It includes several ranges of hills which rise occasionally to over 1,400 ft., and although the scenery consists largely of moorland there are numerous fertile valleys, the different types of country having been brought about by the differences in the divisions of the Jurassic System. The general strike of the beds is in the form of a semi-circle, with the dip towards the centre ; the stratification is noted for its regularity and freedom from major faults.

The rocks of the system are separable into four main divisions, viz., in descending order, the Upper Oolite, the Middle Oolite, the Lower Oolite, and the Lias. The Upper Oolite consists largely of the Kimmeridge Clay shown on the geological map ; the Middle Oolite of the Corallian Series of grits and limestones, Oxford Clay, and Kellaways Rock; and the Lower Oolite of the Cornbrash and Inferior Oolite Series, consisting of grey limestones, estuarine beds, and dogger beds. "Dogger" is a local term for any hard rounded stone, concretionary or otherwise, and the dogger beds are bands of sandstone, limestone or ironstone containing such nodules.

The Lias, consisting mostly of shales, is divided into Upper, Middle and Lower, but the scale of the map does not permit these sub-divisions to be shown. Hence on the map the comprehensive term "Lias" is used and is shown as plain, unmarked spaces. Tt is with the Upper Lias that we are concerned, as one of its constituent beds is the Alum Shale, and a detailed section of this division, measured on the coast between Whitby and Hawsker, is given in the table. The outcrop of the Upper Lias narrows from the western rim of the circle to a thin strip running down the coast, where it forms a long line of imposing cliffs.

Traversing the Jurassic rocks is a basic dyke which runs approximately south-east from the neighbourhood of Stainton and Ayton in Cleveland to Fylingdales Moor near Robin Hood's Bay, where it either dies out or does not reach the surface. Its thickness varies considerably, widths of 20 ft. and 80 ft. having been recorded in different places, and where it has intersected the sediments they have been burnt. The rock is known as whinstone, and although termed basic it has a silica content of about 58 per cent. It is quarried extensively for use as a road-metal.

Drawings and Photographs accompanying the article