John Strachey (1671-1743) was a Somerset squire and antiquary of Sutton Court (Figure 3). In 1719 he made a pictorial cross-section of the geology under his estate, drawing profiles of underground strata seen in nearby coal works, and projecting them according to their measured thicknesses and attitudes into unknown areas between the coal workings. He thus constructed realistic and structurally plausible forecasts of local coal prospectivity. His purpose seems to have been to illustrate his grant of a coal-lease on parts of the Sutton estate, drawn up in that year. "To this day,’ said Sir Edward Bailey, Director and historian of the Geological Survey, "It conveys as clear a picture as could be desired of a semi-concealed coalfield’. Strachey’s stratigraphical cross-sections, of which he published several, are the earliest known in scientific literature.
Some years later, William Smith (1769-1839) working in the same part of this coalfield, also took an interest in the relationships among strata underground. He introduced a new form of map, tracing emergent edges of subterranean strata at the surface of the ground; and even more importantly, he established uniquely and for the first time that among broken or remote tracts of strata, identities among detached parts could be proved by identities among fossils contained within them. It is a historical fact that all present-day stratigraphic practice has an ancestry linked to these events in Somerset.
The brief study here presented sets out to explain the impulse and source of inspiration that caused William Smith to begin his investigations among the stratified rocks of Somerset near Stowey and High Littleton, a few miles south of Bath. The story leads from John Strachey’s first essay on coal-mines to the identification of named strata by means of their contained fossils, as applied by William Smith 80 years later. Both events took place on the same ground, on lands owned by two closely related families.
Literary and historical links between Smith and Strachey have grown much more obvious since suspicion began to grow that the biographical account of Smith compiled by John Phillips, his nephew, was historically inadequate. Indeed, one might infer that sometime during the period between Smith’s death in 1839 and the 1844 publication of Phillips’s Memoirs of William Smith, that a number of vital records had been laid aside or perhaps unconsciously discarded.
Such is the power, even today, of John Phillips’s account of William Smith’s geology, that serious investigation of Smith’s views on the nature and properties of strata, and the sources of his ideas can seem more like memorial bashing than genuine enquiry. Yet questions ought to be asked. For example, did Smith acquire his view of the Strata from his own observations? How did he discover John Strachey’s work? Did Phillips sift out "unsuitable" papers? He had both possible motive and certain opportunity, for Smith died at Northampton, miles from his home in Yorkshire, where he had lived alone. Phillips, as nephew, was next of kin.
Smith’s schooldays
Some notion of his childhood is essential to understanding Smith’s geology. He was born in March 1769, the son of a blacksmith in the Oxfordshire village of Churchill. His schooling, as reported long after by Phillips, was "very limited’. Among the rural poor of that time only a small proportion of school-aged children (c. 1 in 30) received any organised education. The luckiest event that could befall them was to be placed in the apprentice-house of an enlightened employer. At eight years old, an orphan in a small and unremarkable village, sent to work at an uncle's farm, and at risk of becoming yet one more helpless addition to the wretched underclass of child labourers, William Smith became one such lucky individual.
By singular good fortune Smith’s intelligence and industry were noticed by a sharp-eyed land surveyor, Edward Webb of Stow-on-the-Wold, not far from Churchill, who took him in as an assistant. Smith lived with the Webb family for nearly five years, training himself in the disciplines of surveying, measuring, casting numbers, making agricultural valuations, managing improvements to farmland drainage, and assisting with surveys of lands scheduled for enclosure.
It does no disservice to Smith’s achievements to say that he possessed particular qualities of persistence and stubbornness, and that he began his adult years equipped with hardly more than an ability to read, a serviceable longhand, and the bare elements of scripture. The story of Smith’s initial awareness of Earth’s strata, and his indebtedness to the work of John Strachey, illustrate the initial dependence of geological knowledge in 18th Century England on the observations of industrial artisans and workmen.
Chew Magna and Stowey 1719–1727
On 18April 1719, John Strachey granted a 21-year lease on several tracts of his Sutton estate to William Jones of Stowey, his brother-in-law and neighbour. The indenture 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 seams as at Sutton were being worked in pits toward Farrington Gurney, about four miles away to the southeast of Sutton Court. Strachey’s land at Sutton lay between these two known productive areas, and to demonstrate its potential value as a prospect he made a cross-sectional diagram showing his predicted subterranean arrangement of the coal seams, their individual thicknesses and depths. Whether William Jones ever sank a shaft on the Sutton lease is not known.
John Strachey wrote a letter explaining the geology of the local coal industry and the nature of the overlying strata to his friend Robert Welsted MD, a Fellow of the Royal Society. Welsted communicated Strachey’s letter to the Society at its meeting on 7 May 1719, and arrangements were made for the letter to be published together with the cross-section. Strachey was then 48 years old. Later, at the November 5 meeting of the Society he was elected a Fellow. Variants of Strachey’s 1719 diagram were reproduced in 1721, 1725, and 1734, the last two lengthening his original four-mile section to more than 20 miles, crossing a tract from the Chalk hills of Wiltshire to the high ground above Wrington, near Bristol. He also made "strike" sections at right-angles.
In his second paper for the Royal Society (1725), and in a booklet independently published two years later, Strachey emphasised his conception of the strata as a body or group of layered earths and minerals extending across England north-eastward from the coast of Wessex to Yorkshire and the farther coast of Northumberland. The Strata as he then understood them were potentially of global extent:
"All these different Strata, as found in any of those Places I have observed myself, or met with from others, I have at one View represented in a globular Projection of the terraqueous Globe."
The Strata, thus defined, consisted of several discrete entities, as follows: at the top Chalk (Upper Cretaceous), followed downward by Freestone (Upper & Middle Jurassic), Lias and Marl (Lower Jurassic), Red Earth (Triassic), Clives and Coal (Upper Carboniferous), and Limestone with Lead (Lower Carboniferous). This sequence was expanded to 12 units or component parts by the addition of other earths, ochres, and metals, so that the Strata became a duodecimally-layered fabric covering the whole globe. Strachey visualised the rotating Earth as consisting of 24 individual layers, 12 of which were exposed to the passing day, at the rate of one per hour, and a further 12 duplicating exactly the same sequence at night (Figure 4).