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October/November 2003 |
| Feature – Birth Of A Science | |
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Beside the restored Somerset Coal Canal (SCC). Junction with Kennet and Avon canal lies just beyond the bridge.
A pathway now occupies the site of the SCC near Monkton Combe.
William Smith's Tucking Mill House made from oolitic limestone blocks.
The memorial plaque on the right hand side of the wrong building.
One of the numerous locks that replaced the Caisson Locks near Combe Hay.
The country around Combe Hay. The SCC ran along the hill behind the manor house.
The George Inn, Norton St Philip was already 500 years old when William Smith lived in the area.
William
Smith's 1820 version of the geology map reproduced by the British Geological
Survey.
John Phillips' Memoirs of William Smith (centre right) is among Smith material displayed at Museum of Natural History, University of Oxford.
The Geological Lecture Room, Oxford. 1823 lithograph by Nathaniel Whittock (Bodleian Library).
Map
of the SCC and the route taken by Don.
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In
The Footsteps Of William 'Strata' Smith One of the most popular 'geology' books to hit the shelves in the last couple of years, and one I received as a Christmas present from my daughter, was Simon Winchester's The Map that Changed the World. As the subtitle, The Tale of William Smith and the Birth of a Science, indicates, this is the story of William 'Strata' Smith who has been called "The Father of English Geology" and whose 1815 geological map of England and Wales has been credited by some as being the first geological map to be published. Some reviewers of the book put up strong cases against such a claim but, nevertheless, Smith's map was certainly the first geological map of England, Wales and parts of Scotland and probably the first of a whole country. What is not in dispute is the understanding of the significance of fossils and stratal succession Smith developed as he went about his business as a surveyor and engineer throughout England in the late 1700s and the early part of the nineteenth century. One of Smith's earliest introductions to rocks occurred when he went underground in 1792 to examine the Upper Carboniferous coals in the Mearns Pit colliery in Somerset (referred to in those days as Somersetshire). It was in this mine that he first noticed the succession of rock types and that each contained a deterministic set of fossils. In 1793 he was engaged by the renowned engineer, John Rennie, to lay out the route for the Somerset Coal Canal. The canal was to provide a waterway for barges to carry coal from the collieries of the north Somerset coal fields in southwest England to the nearby growing cities of Bristol and Bath, and to the coal-starved rural villages of Wiltshire. The plan called for the building of a canal from a junction with the Kennet and Avon canal at Dundas Aqueduct at Limpley Stoke, six miles from Bath, along the Midford and Cam valleys for ten and a half miles to basins at Paulton and Timsbury, with an arm branching off at Midford following the Wellow valley for seven and a half miles to the collieries at Radstock and Welton. These two branches were nearly parallel, running approximately east-west, less than two miles apart. What's more, the rocks in both the valleys dipped gently to the east so that Smith encountered successively younger rocks as he surveyed the canals in an easterly direction. Smith's observations of the changing rock types and their unique fossils in the two canals lead him to use the concept of stratal superposition that he had developed in the coal mines, to predict the strata that would be encountered as the canals wound their way around the countryside. Furthermore, by joining up the points on a map where the two canals cut the top and base of the various strata and using his knowledge of local rock outcrops, he was able to produce a geological map of the local area. This map, produced in 1799, and referred to as the 'Bath Circular Map' due to its unusual shape, was the first of Smith's geological maps. Over the next 15 years Smith travelled extensively, both for work and at his own expense. Wherever he went he examined, collected and mapped the rocks that so fascinated him. In 1815 his work was compiled into 15 sheets and published under the grandiose title, A Delineation of The Strata of England and Wales with part of Scotland; exhibiting the Collieries and Mines, the Marshes and Fen Lands originally Overflowed by the Sea; and the Varieties of Soils according to the Variations in the Sub Strata; illustrated by the Most Descriptive Names. I have had an interest in Smith's map ever since I was introduced to it in my very first geology lecture at ANU, where the 2.4 m x 1.83 m (8ft x 6 ft) map was mounted on the wall of the lecture theatre. The opportunity to follow in 'Strata' Smith's footsteps in July this year came about when my wife, Maureen, and I were on a walking holiday in England. By coincidence we picked Dundas Lock Cottage, the old lock keeper's cottage at the Dundas Aqueduct, as our Bed and Breakfast when we planned our walk along the Kennet and Avon canal between Bath and Bradford-on-Avon. A search on the web quickly revealed its association with the Somerset Coal Canal. Upon our arrival we found the B&B was run by Tim and Wendy Wheeldon. Tim had been a helicopter pilot in the Royal Navy but left to become a chopper pilot in the Nigerian oil patch. After six years he had obviously made enough money to return to England, and to purchase a parcel of land that included about 1 km (0.621 miles) of the old Somerset Coal Canal at its junction with the Kennet and Avon Canal at the Dundas Aqueduct. At the time of the purchase, the canal was completely filled in and the old cottage was in disrepair. Using money accumulated in Tim's chopper days, the Wheeldons refurbished the cottage and cleaned out and repaired the lock and canal. They also built a marina for canal boats and a visitor centre. Tim told me he had walked and written notes on the entire length of the canals and a couple of years ago made a film entitled, 'Canals to Coal'. With this knowledge, his offer to lend me his set of Ordinance Survey maps on which he had plotted the course of the canals was too good to pass up. So while Maureen took a 10 minute taxi ride to our next evening's accommodation, I set out on a seven hour walk armed with Tim's maps and annotations, some notes I had brought from Australia, and my hand lens, to follow the steps of William 'Strata' Smith. "… easy stroll along pathway beside cleaned out canal leading to marina and visitors centre. Stopped to visit small museum, studied large map and historic photos. "… too early for drink at Limpley Stoke Hotel. "… followed path along abandoned canal. Easy to follow where path ran inside the canal, other places totally filled in. "… detoured uphill to picturesque Monkton Combe, had to wait til 12 for The Wheelwright Arms to open (1/2 pint Adnams Southwolds bitter). "… turned off Summer Lane, leading to Smith's Kingham Quarry, followed country lane beside canal to Tucking Mill." In 1798 William Smith bought a small estate at Tucking Mill midway between Monkton Combe and Midford. Tucking Mill House, which is the building on the land owned by Smith, is located a few hundred metres east of a more ornate and more recent two-storey building which erroneously bears a memorial plaque to Smith. Winchester, who has a degree in geology from Oxford (although he is a journalist and author by choice), explains in his book that tucking is the old word for fulling, which is the process whereby lanolin is removed from wool. The material that was used to achieve this was Fuller's Earth – a Middle Jurassic clay rich in smectite which happens to have the ability to absorb oil. Maybe we should be taking out petroleum licences over the old mill sites dotted all over England! "… followed footpath past Smith's house to look at conjectural route of railway and Inclined Plain from Kingham Quarry. "… returned to Tucking Mill by path behind Midford Castle. "… followed canal towards Midford, examined fossiliferous oolite dug from canal." Much of the area through which this canal was excavated consists of Middle Jurassic oolitic limestone. The honey-coloured rock, known locally as Bath Stone, makes excellent building material and was used extensively in the Georgian buildings in Bath. At the time Smith owned Tucking Mill, Midford Castle was owned by Charles Conolly. In 1819 Conolly had Smith committed to debtor's prison for failing to pay a mortgage he had taken out to help meet the expenses of operating his own Bath Stone quarry – Kingham Quarry. "… resisted stopping at Hope and Anchor Midford for a pint, crossed restored aqueduct. "…crossed packsaddle bridge, followed canal to site of Caisson and Lock Flight." A flight of 19 locks was built to replace the experimental and unsuccessful 'Patent Hydrostatick or Caisson locks'. The caisson lock consisted of a large oval shaped masonry chamber—the cistern—in which a 24.4 m (80 ft) long watertight box (the caisson) was suspended from four giant geared legs. By means of watertight doors, a fully laden boat carrying up to 30.48 t (30 tons) of coal was then floated into the caisson. Once the outer door of the cistern and the inner door of the box were sealed, the caisson was then either raised or lowered 14 m (46 ft) to the next level, where the seals would be opened and the boat allowed to carry on along the canal. It is speculated the caisson lock failed because the Fuller's Earth, in which the masonry chamber happened to be dug, swelled to such an extent when in contact with water, it trapped the caisson! (the 200 year old equivalent of stuck pipe). "… left canal and walked up steep hill into Combe Hay, too late for lunch at The Wheatsheaf Arms, settled for a pint of Courage Best and a packet of chips. "… walked cross country to Wellow and had half a pint of Sussex Bitter at The Fox and Badger. "… crossed Wellow Brook close to abandoned railway line." Only the Radstock to Wellow section of the Radstock canal was ever constructed. In 1814–15 the towpath and proposed route of the remainder of the canal to Midford was converted to a tramway, where teams of three horses hauled eight or nine wagons containing a total of 11.18–12.19 t (11–12 tons) of coal. A later railway line closely followed the path of the tramway and abandoned canal. "… after an hour and a half reached Norton St Philip, staying in The George Inn, dates back to 1300s. Well- earned pint of Kronenberg with a dash. "… wonderful day, beautiful countryside, great walking – in the footsteps of "Strata" Smith." Postscript. A few days later another of my walks ended in Oxford where I spent several hours at the University of Oxford Museum of Natural History. Smith was born in Churchill, a small village close to Oxford. Does that make him Oxfordian? "… small amount of Smith's original material on display, fascinating reading. "… bought facsimile of Smith's 1820 map, education officer gave me postcard of 1823 lithograph The Geological Lecture Room, Oxford showing Buckland lecturing." I suspect much of Smith's material is held by the museum because his nephew John Phillips, whom he had mentored, was a Reader of Geology at the university and then succeeded William Buckland as Professor of Geology. His book, Memoirs of William Smith, was published in 1844, five years after the death of his uncle and 157 years before Simon Winchester brought 'Strata' Smith to the attention of the world and myself again. Further
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