Transactions of the Geological Society, 1st series, vol. 4/Extracts from the Minute Book of the Geological Society
XXXI. Extract from the Minute Book of the Geological Society.
An extract of a letter from Dr. Macdonell, of Belfast, to Mr.
Horner, was read, in which an account is given of a stratum of submarine
peat and timber in Belfast Lough, situated under the level
of ordinary tides, but generally left bare at ebb tides. Nuts are
numerous in it, both on the east and west sides of the harbour.
On the east side, where calcareous rocks exist, the nuts are filled
with calcareous spar, but on the west side, where the rocks are
schistose, they are empty. Some of them are perfectly filled,
others only partially so, yet the shell appears quite entire, and unchanged
by any petrifactive process, although when put into acids
some effervescence takes place. Dr. Hutton alledges that no infiltration
can happen in circumstances similar to that in which these
nuts are placed, for they are immersed in a bed of peat four or five
feet thick, and this covered by a deposit of sand, shells, and blue
clay, and the whole kept moist and all evaporation prevented by
being covered three-fourths of the day by the tide.
1811, January 18.
An extract of a letter from Dr. MacDonnell, of Belfast, to Mr. Horner, was read, giving an account of some granite veins in slate, in the Mourne mountains.
In some part of these mountains, which are situated at the southern extremity of the county of Down, grey granite forms the summit of the mountain, and primitive slate the sides. The contacts are as sharp as possible, without the least of one rock graduating into the other, and in all cases the granite is continued from the great mass in veins through the slate, but never the contrary.[1] Masses of slate often occur, like islands floating in, and surrounded by the granite of the veins. Mr. Playfair, who was with Dr. Mac Donnell, remarked that the schist, which lies upon and near the granite, has a much greater number of fissures than that which is a mile distant. The granite veins generally terminate in fine threads.
1811, November 1.
A letter from George Cumberland, Esq. of Bristol, was read, giving an account of a trap rock that had been discovered at Micklewood, in Gloucestershire. It occurs to the east of the road going from Bristol, within two miles of Frampton, on an estate belonging to Lord Berkeley, and is known by the name of the Old Raock. The mass rises perpendicularly to the height of about 30 feet, is less than 300 yards wide, and extends in the other direction about a quarter of a mile. The same rock is found again to the north-east of the first mentioned place, dipping to the east beneath the surface.
The Micklewood rock has an amygdaloidal character, containing
plain or striped chalcedonies, and numerous fungi form or irregularly
cylindrical masses, composed of iron spar. Those masses
are often found two feet in length; the chalcedonies vary from
one to twenty inches in diameter, and are nearly all of the same
shape, convex above, and concave beneath.
1811, November 1.
An extract of a letter from Dr. Murray, of Harrogate, to Mr. Sowerby, was read, mentioning that sulphate of strontian had been found in limestone on the banks of the Nidd, near Knaresborough.
1812, March 6.
A notice by Arthur Aikin, Esq. was read, on a green waxy substance found in the alluvial soil near Stockport, in Cheshire.
In 1811 a specimen from the above mentioned place was communicated to the Society by Dr. Henry. On a chemical examination Mr. Pepys found it to be a combination of resin and oil mixed with a quantity of brown quartzy sand. Its colour was bluish green, and was at first supposed to be occasioned by copper, but no metallic matter except iron was discovered in it. From its composition, and the small depth at which it was found, it was not supposed to be a natural product, but Mr. Aikin is inclined to doubt this conclusion, having met with, in the Dictionnaire d'Histoire Naturelle, under the article Sabliere, an account by M. Patrin, of the discovery of a similar substance at the foot of the hill of Menil Montant, near Paris. It there occurs in sand, accompanied by fresh water shells.
1812, June 19.
A notice by C. Mackintosh, Esq. on the albuminous strata at Campsie was read.
The coal formation which the Scottish albuminous strata accompany, may perhaps be traced and identified in four distinct points of this particular district of Scotland, namely, Campsie in Stirlingshire, Kilpatrick in Dumbartonshire, and Hurlet and Houston, in Renfrewshire. The strata of the four places vary indeed in thickness, but their position and alternation may be considered the same. A sketch of the Campsie strata is subjoined, as descriptive of the whole.
| After passing through the soil and one foot of limestone, alternating strata of Bituminous Schistus and ironstone occur, till we arrive at the immediate vicinity of the albuminous materials; which are, | ||
| Limestone | 4 | feet |
| Aluminous schistus, which consists of (what the miners call) the gentle slate, and the diamond slate | 2 | |
| Coal, of the caking quality of the Newcastle, which contains the slaty and the nodular pyrites | 4 | |
| Fire Clay of excellent quality | 1 | |
The coal has been extensively excavated for a long series of years, from mines of which the temperature is seldom under 60° Fahr. frequently as high as 80°, in places excluded from any direct current of air. The circulation of this warm air has ripened the hard slate into various qualities, and these contain proportions of alum and copperas, which vary according to the time of their exposure, the recent slates abounding in copperas, those longer exposed, in albuminous matter.
1815, April 7.
A notice was communicated by Leonard Homer, Esq. respecting the rocks of the Isle of Tino, in the Archipelago.
The highest part of Tino is one long ridge of limestone, which affords excellent marble, that is sent for grave-stones to Smyrna and Constantinople. In the garden of an Italian convent there is a beautiful vein of asbestos running through serpentine, which passes into a kind of verde antique. Ut is stratified and dips westward about 65°. Here are many rich veins of lead, which generally occur in large veins of quartz in sandstone. The schistus of this island, on the side opposite to Andros, is well calculated for slates; that opposite Miconi is very micaceous.
1815, November 3.
Dr. Traill presented to the Society some magnetic iron sand, mixed with much iserine, accompanied with a letter, of which the following is an extract.
“ I send you a bag filled with magnetic iron sand, mixed with much iserine, which I discovered more than two years ago in the hundred of Wirral, in Cheshire. It occurs on the shores of the Mersey, opposite to Liverpool, at Seacome Ferry. After heavy rains it oozes out of a deep bank of clay; but I strongly suspect that its matrix is the coarse reddish brown sandstone of the country, which, near Seacome, contains many quartzy nodules.”
In a subsequent letter (dated 26th October, 1816) Dr. Traill says, “ After the heavy rains of this summer, I have traced the magnetic iron sand and iserine for several miles along the coast. They are washed out of a bed of cohering sand that lies below the clay, and may be considered as entering largely into the Geological composition of that part of Cheshire.”
1815, December 15.
A Letter from the Rev. Archdeacon Barnes was read, dated Bombay, March 31, 1815. In this letter Mr. Barnes communicates, on the authority of Mr. Copeland, Assistant Surgeon to the European force in the Guzerat, some particulars relative to the carnelians of Cambay.
These are all procured from the neighbourhood of Broach, by sinking pits during the dry season in the channels of torrents. The nodules which are thus found lie intermixed with other rolled pebbles, and weigh from a few ounces to two or three pounds. Their colour when recent is blackish olive passing into grey. The preparation which they undergo is, first, exposure to the sun for several weeks, and then calcination. This latter process is performed by packing the stones in earthen pots, and covering them with a layer five or six inches thick of dried goat's dung; fire is then applied to the mass, and in twelve hours time the pots are sufficiently cool to be removed. The stones which they contain are now examined, and are found to be some of them red, others pink, and others nearly colourless, the difference in their respective tints depending in part on the original quantity of colouring matter, and in part, perhaps, in the difference in the heat to which they have been exposed.
1816, January 5.
A communication from J. Taylor, Esq. Member of the Geological Society, on some remarkable appearances in coak, was read.
The coak in question is produced from two varieties of Newcastle coal, known in the market by the name of Tanfield moor and Pontop. The coal is charred in an oven of brickwork, of very simple construction, each charge being sufficient to cover the floor to the thickness of 18 or 20 inches. The combustion begins at the surface and proceeds gradually downwards. When all the bituminous matter has been driven off; the mouth of the oven is opened for the purpose of drawing the charge, at which period the coak presents the appearance of a glowing pavement rifted into perpendicular columnar masses, the bases of which rest on the floor of the oven. Adherent to the sides of these rifts are occasionally found concretions of a rather flat and small botryoidal external figure of an iron black colour, and highly metallic lustre, resembling grey manganese, or black hematitic iron ore.
Intermixed with these are small arborescent tufts, about a quarter of an inch in length, adherent by their base to the mass of coak, each branch of which, when examined by the microscope, appears composed of minute botryoidal shoots.
- ↑ Pl. 28, fig. 1.