Geoscientist Online

Notes for field excursions to the birthplace of stratigraphy

Descriptive notes on the sites to be visited are presented below as an itinerary scheduled to begin at Sutton Court at 10.00 am. and to end at Tucking Mill, Midford. at 3.00 pm.

Stop 1, Sutton Court

‘This old house is of no importance in itself, it is no Longleat or Hatfield, yet it touches the main course of English history, from the time of Edward the Confessor to the present day ... And so long as the old walls remain there will be two or three persons in each generation in whom they will awaken and keep alive a sense of the reality of English history which cannot be got by books alone.’

Fig. 1. Sir Edward Strachey, Bt., 1895

Approaching Sutton Court from the Chelwood crossroads, about a mile south of Pensford, arable fields reveal red Triassic soil which here overlies Coal Measures (see map). Signposts to the right indicate ways to the old coal-mining areas of Stanton Wick and Stanton Drew; and beyond them are elevated tracts of Lower Jurassic, such as Dundry Hill, capped by Middle Jurassic (Inferior Oolite) limestone.

Until 1973, Sutton Court was the residence of Sir Edward Strachey (1882––1973), second Baron Strachie, and last in direct line of descent from John Strachey, F.R.S. The house still appears much as it did in former times, though it is now a multi-apartment condominium. Viewed from the main avenue approaching the house from the north, the outer wall and the tower with its prominent stair-turret were part of a 14th-century castle. The buttressed wing to the left (northeast) was an Elizabethan parlour and chapel. Most of the stonework has the colour and appearance of Carboniferous Pennant sandstone, probably from quarries at Temple Cloud, nearby. Much remodelling took place in the mid-nineteenth century at the hands of Sir Henry Strachey and his architect Thomas Wyatt.

John Strachey was born here on May 10, 1671. He inherited the estate at the age of three, and was educated at home. He spent a short time at Oxford and the Middle Temple, and later took up lifelong interests in what were then called ‘antiquities’. In 1719, at the age of 48, his first geological paper was published by the Royal Society. It included a detailed stratigraphical cross-section of the country around Sutton Court, described below.

Fig. 2. Strachey's Section of the Strata, 1719

Strachey's cross-section (see diagram) represents strata both underground and at the surface along a line beginning near Stanton Drew and extending southeastward in the direction of Farrington Gurney. It was the first measured horizontal section to appear in English geological literature. Strachey specified twenty-two subdivisions of strata, including thicknesses for all but two of them, descending from Lower Jurassic at the ground surface, through Triassic to a point about 300 feet into the Upper Carboniferous. Such discriminating observation and measurement was altogether new and original. At first sight, the section may seem somewhat crude, though closer inspection reveals that it is certainly not. For example:

(a) Strachey says in his 1719 paper that in the area discussed all the coals ‘pitch or rise about twenty-two inches in a fathom,’ which is a slope or dip of 17°. Measuring the illustration will reveal that the engraver varied slightly from 17° to 19°. Modern Geological Survey maps show 18°.

(b) Most of the subsurface geology illustrated could not have been observed at the surface, and was revealed by correlating strata underground, from coal-pit to coal-pit.

(c) Strachey's thickness measurements of the coals and intervening strata found in pits at Bishop Sutton (half a mile from Sutton Court) accord very well with later observations. The collieries to which he referred had disappeared before the 19th Century, though it is plain from records of these nearby pits that Strachey’s measurements were accurate, and that names he used for individual strata continued in use until mining ceased.

Why did Strachey collect all this detailed information to be represented on his diagram? For anyone interested in coal it would have explained the exploration prospects on the Strachey estate. An important clue to such a motive came to light with an indenture dated April 18th, 1719, stating that John Strachey granted a twenty-one year lease on several tracts of his Sutton estate to William Jones of Stowey, who was both his immediate neighbour and his brother-in-law. The lease allowed Jones ‘to Search for open dig or Sink any pitt or pitts for Coal.’ Strachey had studied the coal workings at Bishop Sutton, about half a mile southwest of Sutton Court, and at Stanton Drew, about a mile to the north. He had learned from colliers that the same coal seams were being worked in pits toward Farrington Gurney, about four miles southeast of Sutton Court. Strachey’s estate at Sutton lay between these known productive areas, and though coal-measures were not exposed on his land (being hidden under red Triassic soil) Strachey’s diagram demonstrated great potential value to a coal prospector.

Whether William Jones ever sank a shaft on the Sutton lease is not known, but less than three weeks after the contract was signed, Strachey’s written description of the coal mines in this area of Somerset was presented at a meeting of the Royal Society in London.

Professor Desmond Donovan, visiting the area in December, 1987, made these further comments:

‘Strachey's section also shows shafts commencing in (Blue) Lias, and therefore penetrating the whole thickness of the Trias; the shaft at the right-hand (NW) end of his section would have had to sink through about 200 feet of Mesozoic before reaching Coal Measures.

Strachey wrote (1719, p.968) that his section was about four miles long and extended from NW to SE. This raises several points. The section is probably idealised, but if it is not wholly imaginary, then the NW end must be at the southern slopes of Dundry Hill, where the place-name Blacklands (ST 582641), on the Blue Lias outcrop, does indeed suggest the presence of old coal tips. The right-hand valley in the section would then be the Chew valley at Stanton Drew, and the left-hand one the Cam valley. The fault (‘Ridg’) could be the Clutton Fault.

The seams listed by Strachey agree in a general way with the Bromley seams, the Peacock or Peau Vein, with ‘cockle-shells and fern branches’ in the ‘cliff’ above it being perhaps Bromley no.4, which has fossil plants and Anthraconauta in the shale above it (G.A.Kellaway, pers. comm.). Strachey's Stinking Vein, the highest, would be Bromley no.1, and so on.’

The Coal Canal

Late in 1792 proposals were made in the district for a canal to serve the mines, and a newly formed Canal Committee, having received favourable reports of William Smith's surveying work on Lady Jones's properties, engaged him in 1793 to take levels along the proposed route of the canal (map). The line as originally projected was to extend south-westward from a junction with the Kennet and Avon Canal, to pass along the valley of the Cam Brook by Midford and Dunkerton into the mining area near High Littleton. A branch of it, leaving the main line at Midford, was to go farther southwest on a higher level, to serve collieries in the Radstock area. This branch never reached completion, and was terminated near Lower Twinhoe Farm (ST 756 594). A tram road was later constructed from Radstock to Lower Twinhoe on the towing path beside the unfinished canal, and was continued from there down to Midford, where by means of a wharf at the end of the tramroad and a small aqueduct the collieries near Radstock were connected to the Kennet and Avon waterway (Map, Inset B).

The main, or northern branch of the coal canal terminated at Timsbury Basin, by Paulton Engine pit in the Cam valley, midway between Rugbourne and Paulton village. Paulton Engine Colliery, the earliest after Mearns in this part of the coalfield was working in 1791, when Smith arrived at Rugbourne. It had an atmospheric or ‘fire’ engine to lift water from a depth of more than 600 feet. After the canal was built, wharves at Timsbury Basin received coal carried by tram roads from nearby mines. Nine pits were connected from the southern side, and nine others from the north, of which Mearns was one. Tenders for constructing tram roads up to Meams pit were invited in May and July of 1795. Movement of coal from the Timsbury terminus to Dunkerton Wharf began in November, 1799. Paulton Engine Pit closed in 1869, after eighty years in work.

Stop 4, Dunkerton Wharf and the Fosse Way.

Opposite the public telephone box, 250 yards uphill from the Old Swan, on the east side of the road, the line of the Coal Canal is clear, its bed filled with rubbish and weedily overgrown. For two centuries the Parliamentary six-milestone stood here on the canal bank by the road. Follow the towpath for 150 yards to the intersection with an old bridle-road, now a public footpath. This is the site of a former bridge over the canal, on each side of which were coal wharves. This was the first section of the canal brought into operation, when in October, 1798, coals from Camerton were unloaded here and taken by pack-animals down to Bath.

The old bridle-road going uphill from Dunkerton Wharf is the Fosse Way, an immensely long 400-mile Roman alignment connecting Axminster in Devon with Lincoln and the country beyond. The Fosse Way was not one of the roads radiating from London, but a cross-country means of military communication that would have been wanted by the occupying forces at an early stage of the Claudian conquest in AD 47. It consolidated a frontier separating what was securely Roman from what was not.

Stop 5, Dunkerton, the Old Swan Inn

This house, now tastelessly disfigured, was once an inn for travellers on the Fosse Way. It is the actual place where William Smith, on January 5, 1796, wrote his momentous observation on the occurrence of fossils: ‘That wonderful order & regularity with which Nature has disposed of these singular productions and assigned to each Class its peculiar Stratum.’

Smith evidently meant what he said, for he re-worded it on another piece of paper, writing ‘the Creator’ in place of ‘Nature.’ Yet as a working principle, Smith applied the converse of what he had written_–– not that the stratum gave its identity to the fossils, but that the fossils gave their identity the stratum. The fossils were thus identifying the stratum. This point is not trivial, for claims made about Smith’s work are not always consonant with what he actually wrote and did.

By following the progress of construction on the canal it is possible to give a particular reason for Smith’s being here at this time. Tenders for excavating the bed of the canal were called in two-mile sections starting from Paulton Engine colliery in May 1795, and from Radstock on the more southerly branch. Both sections were on Triassic bedrock (the unfossiliferous Red Marle). The next part of the main line, for which a contractor was engaged in September of the same year, extended to the Dunkerton Swan, and was cut mainly in Lower and Middle Jurassic strata__–– Lower Lias, Midford Sand, and Inferior Oolite. By the end of 1795 Smith, who was officially ‘the Surveyor’ would have been aware from his instrumental levelling that distinctiveTriassic and Jurassic strata exposed by the excavations were dipping gently in an easterly direction, each one in turn dropping below the plane of his surveyed level.

Stop 6, Boyling’s Cottage, Combe Hay

To overcome the elevation difference between the upper and lower levels of the main canal, amounting at Combe Hay to about 134 feet, a novel method of moving boats from one level to the other by means of hydraulic caisson lifts was to have been introduced. One example was built by Rowley Farm at the ed of the upper level, near Combe Hay. It operated with a closed wooden vessel or caisson within a vertical water-filled shaft. The caisson was made to carry inside it a 70-foot canal-boat. After several successful trials, the masonry lining of the shaft shifted, trapping the caisson and the boat in it. The problem was geological, not mechanical, due to swelling bentonite in the Lower Fullers Earth beds, which cracked and dislodged the stonework lining the shaft, so obstructing the vessel's passage, and by loss of water paralysing the hydraulic balance. This set-back was financially crippling, and William Smith, as resident surveyor of the works, was deeemed responsible for the failure, though its root cause at the time could hardly have been foreseen. Nevertheless, at the age of thirty, Smith found himself no longer employed by the Canal Company.

Subsequently, the two levels of the Canal were linked by an inclined-plane (Map and picture) on which coal was trans-shipped by means of counter-balanced carriages, coal going down and empties coming up. The coal was moved in bins, each weighing about a ton, pre-loaded at the pit-head. It was a tedious system, laboriously inefficient, and was by-passed in 1804 by a set of conventional locks.

Broadfield Farm, near Hinton Charterhouse.

Broadfield Farm, about a mile south of Midford, was the home of William Smith's brother John from about 1804 to 1819. John Smith was a land surveyor and drainer also, and assisted William in professional engagements. Many of Smith's letters surviving from this period were written from Broadfield Farm, which was a refuge in which he could shelter from his financial problems at Tucking Mill.

Stop 7, Farleigh Hungerford

William Smith's good friend and supporter Benjamin Richardson was Rector of Farleigh, and there are two memorial tablets to him in the Church. Some thirty years after Richardson had been with Smith on Dundry Hill looking at fossils, he was asked to describe his experience. Below is part of Richardson's letter to Sedgwick, then President of the Geological Society. It was written just before the Society made Smith the first recipient of its most prestigious award, the Wollaston Medal:

‘Farley Rectory 10th Feb. 1831

I am requested to present you the particulars of my acquaintance with Mr. William Smith, well known by the appropriate appellation of ‘Strata Smith.’ At the annual meeting of the Bath Agricultural Society in 1799, Mr. Smith was introduced to my residence in Bath, when, on viewing my collection of fossils, he told me the beds to which they exclusively belonged, and pointed out some peculiar to each. This, by attending him in the fields, I soon found to be the fact, and also that they had a general inclination to the south-east, following each other in regular succession. ... He wished me to communicate this to the Rev. J. Townsend of Pewsey (then in Bath) ... we were soon much more astonished by proofs ... that whatever stratum was found in any part of England, the same remains would be found in it and no other.

I am. Sir, &c., B. Richardson’

The Rectory from which this letter was sent is next to the church. John Phillips (1800-1874) Smith’s nephew and first biographer lodged here as a schoolboy. Like Smith, he had been orphaned in childhood, and partly through the good offices of Richardson attended school at Holt, about four miles from Farleigh. Phillips spent a year here with the Richardson family, from 1814 to 1815. The house is now an ordinary private residence. .

Stop 8, Pipehouse.

High on Midford Hill at Pipehouse, three quarters of a mile ESE of Midford village, William Smith demonstrated his method of relating detached outliers or insular hills to the main body of a parent stratum (map with succession). In this example, dating from about 1805, he discusses the Combrash, which was an additional stratum lying between units 3 and 4 of his 1799 standard succession.

‘This point ... has about 7 or 8 acres of the Cornbrash Stratum on it [part of unit 4 of his 1799 standard, unit 7 of his 1813 version]. It is ... in the angle of the pasture Field which goes down to Pipehouse .. .It produces a small piece of good land which ... is common to the soils of the same Stratum about Wolverton [Woolverton, 4 mi SSE] and other places. It was by the extraordinary appearance of this Pasture on the 1st March that I was induced to look for these Fossils well knowing that no Stratum but the Cornbrash could produce such Herbage in a situation where Dung is seldom or ever used. The badness of the Land upon the Clay Stratum which is next down the slope gave strength to the Conjecture and the Inspection of the Stone thrown out of the Farm ditch furnished the most indubitable proofs [i.e. fossils] of what I had expected to find.’

Later, Smith added:

‘The Cornbrash, though altogether but a thin rock has not its organized fossils equally diffused, or promiscuously distributed. The upper beds of stone which compose the rock, contain fossils materially different from those in the under. Near Pipe-house the encrini [Pentacrinus ossicles] are above the springs in the brownish clay [top of unit 8 of his 1813 standard] turned up by the plough.’

Detection of two suites of fossils within a 10-20 ft thickness of Cornbrash, particularly after having determined at Pipehouse that here beneath the vegetation was a detached remnant of it, is one of Smith's most perspicaceous observations. The two suites now form the basis for a Stage boundary in the Jurassic, and the tiny outlier duly appears on Geological Survey maps.

Stop 9. Tucking Mill

Joan Eyles explained in 1974, to anyone who would listen, that:

‘The property called Tucking Mill, in the parish of Monkton Combe near Bath, purchased by William Smith in 1798, still exists, but bears no mark of identification. The nearby Tucking Mill Cottage, in the parish of South Stoke, which bears the tablet Here lived William Smith ... is now known to have been wrongly identified as his home.’

Suspicions existed that all was not right long before Joan Eyles went into print, for the Cottage presents a Gothick style of fenestration and a wrought-iron porch that was more typical of the 1830s than any time before 1798. The crucial facts exposed by Joan Eyles were discovered in the property deeds of Smith's actual purchase, revealing that the wrongly chosen and memorialised Tucking Mill Cottage was in the adjacent parish. Many earnest words have accumulated over the subject of moving the memorial stone to its 'correct' location, but this muddle, now lacking suffiicient apathy to die naturally, has now become its own memorial.

The house that Smith bought in 1798, while employed by the Coal Canal Company was a narrow structure faced with precision-cut ashlar. Some time afterwards the house was doubled in size, more or less, and re-roofed. Of the building as it now appears, the western side (left from the road) was, according to Joan Eyles, Smith's original purchase. This has been disputed by Professor Torrens, quoting a builder’s letter to say that the eastern half was original. On the other hand, the exterior masonry offers intriguing contrary evidence.To the right, the additional structure is made of reclaimed material, of lower quality than the original. Note the string-course inserted at the second-floor window-level, bringing the newer work into line with the older. Speculatively, it seems quite possible that this stone was taken by Smith himself from the abandoned caisson works at Combe Hay, and re-used by him to make an extension to his newly acquired house.

Smith lost possession of the property when his stone-quarrying operations on Combe Down failed, and claims for unpaid debt were made against him by a landed creditor, Charles Conolly of Midford Castle.

Road Directions from Bath or Bristol

From Bristol or Bath, leaving about 9.30 am. Proceed to Chelwood crossroads, intersection of A37 and A368 (ST 625619). At crossroads proceed west 1.75 mi. on A368 to minor road on right. Turn right, and Sutton Court entrance is on left. This is Stop 1, time 10.00-10.25.

Return to A 368, turning right. Proceed 0.5 mile to Stowey turn-off on left. Proceed 0.5 mi. through Stowey village to Church at right. Pull in at farm gate, Stowey House Farm. This is Stop 2, time 10.30-11.00.

Leave Stowey House, continue uphill about 0.5 mi. to minor junction, turn left, proceed about 1 mi. to junction with A 37. Turn right, continue south 1.5 mi. to White Cross traffic lights. Turn left to A 39, signposted to Hallatrow and High Littleton. Proceed about 1.5 mi. to High Littleton. Pass church on right, about 200 yds, fork right at lane (the Batch). Keep left for 200 yds. Park in Recreation Ground on left. Rugbourne Farm; this is Stop 3, time 11.15-11.35.

Return to main road A 39. Turn right and proceed 1 mi. to junction with B 3115. Sign usually obscured, but note used-car sales display. Turn right and proceed about 5 mi. via Timsbury to junction with A 367. Turn right at junction and proceed about half mi. to lay-by with phone box on right. Park at lay-by; Stops 4 and 5, Dunkerton The Old Swan. Time 12.00-12.40.

Leave lay-by, turn right and continue downhill to the Old Swan. Turn sharp left by stone wall into minor road. Proceed about 1.25 mi. to Combe Hay, and continue further 0.25 mi. to Rowley Farm fork (not a stop). Continue down hill 0.5 mi. to old railway viaduct on left. Pull over and park. Boyling’s Cottage.This is Stop 6. Time 12.50-1.00 pm.

Continue along the lane about 1 mi. to junction with B 3110 at Midford, turn right, proceed about 100 yards to Hope and Anchor car park. Five minutes R&R here if wanted, or at The George, Norton St Philip. From Milford continue 3 mi. on B 3110, pass Broadfield Farm on right (not a stop) through Hinton Charterhouse to Norton St Philip, turn left to A 366. One mi. to A 36 (T). Cross A 36 and continue 1mi. to Farleigh Hungerford. Turn right opposite Farleigh Arms and pull in by Church–– St Leonard’s, Farleigh, Stop 7. Time 1.30-1.55.

Return to A 36 (T), turn right, then 2 mi. to Pipehouse, minor side road on left. Turn round at end of lane, about 0.3 mi. This is Stop 8. Time 2.10-2.20.

Return to main road and turn left. Proceed 1.5 mi. to traffic signals at foot of Brass Knocker Hill. Turn left and then left again to pass Monkton Combe School. At end of School buildings turn sharp left into lane posted to Tucking Mill. Continue about 0.5 mi. from the School to Tucking Mill House and draw in at gates to Wessex Water Authority works. This is Stop 9. Time 2.35-2.50.

Depart Tucking Mill at latest before 3.00 pm. Continue west 0.7 mi. to junction with B 3110 at Midford. Turn right to Bath. Proceed uphill about 1.75 mi to junction with A 367. Turn right, follow road signs down to meet the Bristol Road, A 36 (T).

© J.G.C.M. Fuller, 2006.