soft Matter, wherein he put down his Candle, which burning down to this Substance, it melted and burnt; what remained he took Home, took it out of Stone into a Saucepan and melted it; then it was an exceeding fine clear Balsam without Smell, except when thrown into the Fire; but when cooled again, it hardened like fine Fat; several others of those Stones they broke and found them full of this Substance, wherewith they provided the Neighbourhood a pretty Time for greazing Boots and Shoes, till they found it quickly shriveled them up and burnt them to pieces; great Pity such a fine Bitumen or Oleum Terra had been thus wasted." Pilkington * states further that rock-oil has been found in the Black Marble at Ashford, and in a mass of lead-ore at Ashover, and that at Stoney Middleton the miners used to burn it in their lamps. In Stoke Sough, according to Farey,† rock-oil was found, which was set light to, and floated away on the water burning, thus giving rise to a rumour that a burning spring had been found. Much was found also in the Mag Clough Level, which unwaters the Lady Wash Mine.‡ In addition to the explosions of fire-damp referred to by Short, we have a record by Pilkington of several persons having been killed by an explosion of "inflammable air" in driving the Hillcar Sough, near Youigreave (op. cit. p. 174).

Bitumen may now be observed in two forms, the first hard, black, and with a shining surface, the second soft and sticking to the fingers. Analyses by Prof. Johnston yielded the following results :--§

Both the brittle and the elastic varieties occur in the Windy Knoll quarry, 1 miles west of Castleton. The brittle variety may be seen also in the spoil heaps of the Millclose Mine, near Winster, and of the Gregory Mine, at Ashover. It is frequently found also filling cavities in the limestone, (such as the interior of fossils), as in a quarry on the Hopton and Wirksworth road, a quarter of a mile west of the former village. Farey relates (op. cit. p. 175) that a vein, found in the toadstone north-east of Hopton Hall in 1796, in cutting the Via Gellia road, was six inches wide, and filled with a bright, spiry, and dicey "coal," very inflammable, and having thin septa of spar. He supposes it to have been indurated bitumen.

A View of the Present State of Derbyshire, 1789, p. 177. He refers also to a liquid as red as blood, found in small cavities in the toadstone on Tideswell Moor (p. 57), but whether this was a rock-oil or not remains uncertair..

† Op. cit., vol. i. p. 467.

A. H. Stokes, Economic Geology of Derbyshire.

§ Phil. Mag., ser. 3, vol. xiii. p. 22, 1838,

Other Minerals.

Chert.-A stone, which is sold under this name, is quarried near Bakewell and on Longstone Edge. It is more truly intermediate between limestone and chert, being a limestone that has been partly replaced by chert. In some cases the fossils have been silicified, while the stone itself is traversed by a vast number of threads of silica, or even converted wholly, for short spaces, into silica. In other cases the chert occurs in nodules and lenticular masses, imbedded in limestone. The rock is raised for use in the grinding mills in the Staffordshire Potteries. Large blocks of Derbyshire chert are dragged round upon a pavement composed of Welsh chert.* It is said that the fact of the Derbyshire blocks consisting of a mixture of two rocks of different hardness causes them to travel more smoothly than if they consisted of chert alone. Blocks of pure chert would be apt to "suck" through fitting too closely to the floor of the mill, and to travel in jerks.

The chert is being raised in the Deep Rake on Longstone Edge, the limestone forming the walls of the old opencast workings at the east end of this vein having been to a great extent converted into silica in the neighbourhood of the vein. It is also quarried underground near Bakewell, while a quarry has lately been opened on the Buxton Road, three miles from Bakewell, in a limestone containing numerous silicified shells and corals, and traversed by a network of fine interlacing threads of silica. The stone is quarried in blocks measuring about 2 × 14 × 1 feet, and fetches about 17s. a ton.

Calcareous Tufa. -This rock is quarried for use in ornamental rockeries. It is worked in Bonsal Dale, near the Bakewell and Buxton Road, from whence it is delivered at Hassop at 16s. a ton. It consists of a mass of amorphous carbonate of lime, which has been deposited around twigs, leaves, moss, shells, &c. by hard spring-water. The vegetable subtances have generally decayed away, leaving the stone in a very porous condition. A great mass of tufa overhangs the road at Alport, formed in all probability by some spring, that has been diverted by the lead mining. Farey states that a portion of this tufa has been changed to chert. Large quantities of this rock were formed by the warm springs at Matlock, before they were confined in artificial channels. It has been used in buildings.

Rotten-Stone.-This substance has been worked from time to time (according to the demand) on Bakewell Moor and north of Ashford. It occurs also at Wardlow Mires. It has been described by Mr. W. Martin, from whose paper the following notes are taken. It is found in a hollow in the limestone, under the soil, in lumps which sometimes contain nuclei of black limestone, and fossils such as are found in the black marble. It is a dry indurated stone, almost greasy to touch. It appears to be a decomposition product of the black marble. Two varieties, No. 1, very hard and approaching black limestone in appear

*The Welsh chert is a purely siliceous rock, of Millstone Grit age. See The Geology of the Coast adjoining Rhyl, Abergele, and Colwyn (Geol. Survey Memoir). † Op. cit., vol. i. p. 415.

Mem. Lit. and Phil. Soc. Manchester, ser. 2, vol. ii. p. 313-327, 1813.

ance, and No. 2, very soft and earthy in texture, gave the following analysis:

Derbyshire Marbles.-Several varieties of limestone are sawn into slabs and polished at the Marble Works at Ashford,* for the construction of chimney-pieces, &c. The principal are Black, Rosewood, Coralline, Bird'seye, Fossil, and Russet marble. The famous Black Marble is a thin-bedded, earthy, and bitumenous limestone, with conchoidal fracture. It weathers grey, but, when polished, becomes a dense black. It contains lenticular patches of black chert along certain lines, which are of course avoided in the sawing. It occurs in beds of one to fourteen inches thick, separated by bitumenous shales. According to Mr. Martin (op. cit.) it contains about 18 per cent. of alumina, with small proportions (not exceeding 4 per cent.) of silica and (not exceeding 1 per cent.) of iron. The Rosewood Marble is a striped limestone; the Coralline, a grey mottled limestone; the Birdseye, a black limestone dotted with small white encrinite stems; the Fossil Marble is a grey encrinital limestone, and the Russet resembles Birdseye, except in colour. Red and white marbles do not occur in Derbyshire, but are imported when required. The polishing, as well as the sawing, is performed chiefly by water-power. Sand, a fine, micaceous sandstone, emery powder, and puttypowder, are used successively in the process. The cost of a complete fireplace is about 257.

Limestone. The quarries are too numerous to be separately mentioned. Among the principal are those of Miller's Dale, Doveholes, Wirksworth, and Crich. The royalty ranges from 11⁄2d. to 3d. a ton. Black limestones, and amongst them the Yoredale Limestones, have been used in the manufacture of hydraulic cement.

* I was indebted to Mr. J. Twig for facilities in examining these works. †This stone has been sawn at Ashford since the year 1748 (A. H. Stokes, Economic Geology of Derbyshire). It was erroneously stated in the Explanation of Horizontal Section, Sheet 42, to lie in the lowest group of the Yoredale Rocks; it lies about 200 feet below the top of the limestone.

APPENDIX I.

LIST of FOSSILS from the CARBONIFEROUS LIMESTONE of
DERBYSHIRE and NORTH STAFFORDSHIRE.

Drawn up by R. ETHERIDGE, F.R.S.

Revised and greatly enlarged for this Edition by G. SHARMAN, and E. T. NEWTON, F.G.S.

THE list given in the former edition has been revised and a number of species added. The latter are largely derived from the Carrington Collection, now in the Museum of Practical Geology, and are mostly from Wetton, Gateham, Narrowdale, Alstonfield, and Beeston, localities close to the border of Derbyshire, and included in the one column marked North Staffordshire. An asterisk is placed before those species which were not contained in the previous edition.

The column headed "Derbyshire" includes specimens that cannot be more nearly localised.

The famous locality of Longnor, in North Staffordshire, is included in the column with Park Hill, Derbyshire, because it is believed that most, if not all, the specimens said to come from Longnor are really from Park Hill, which is only a short distance from Longnor, but across the county boundary.