London Stock Bricks in the Bazalgette sewers: inadvertent excellence? [speculative connections/ manifest virtues]

Over 300 million bricks were used in the construction of the Bazalgette sewer system for London. During the construction period there was a huge demand for bricks (and bricklayers) and the prices rose considerably. The obvious source of bricks was the multitude of brickworks around London all producing the London Stock brick- the classic brick made from the local brickearth.                                                                                                                                                                                                           

                                                                                                                                              

These bricks had certain properties and virtues- it appears that they were well suited for sewer construction. How many of Bazalgette's 300+ million bricks were London Stock bricks? It would seem logical that most of the Bazalgette bricks were London Stocks.

Was Bazalgette aware of all the excellent properties that LSB possessed and that made them specially suited for a complex drainage system, or did he take an 'overall' view of construction bricks and not distinguish with particular care among the various types- for such a careful engineer this latter approach seems unlikely?

It is possible to list a set of remarkable advantages that the LSB possessed; an excellent range of properties which has contributed to the success and longevity of the sewer system. The range of virtues is impressive: moulding and making virtues, strength virtues, dimensional virtues, chemical virtues, geographical virtues, etc..

Moulding and Making

The handmade brick is made in a mould. Each single brick is formed from brick material which is pressed into the mould by the moulder. He (invariably he) presses the material into the mould using the adequate and learned amount of force. This to some extent compacts the material and establishes the initial particle structure- a modest tensile strength develops as compression enhances particle contacts- the brick can now be handled and moved to a drying region. 

The BE(as ground material) has a packing density P of perhaps 0.5, which is a voids ratio e of 1.0. Half of the space is taken up by solid mineral material, half of the space is space. If BE is compacted (remoulded and then compacted)the P value rises to perhaps 0.6-0.7- and this P value stays relatively high even after firing. The actual density of a typical LSB is around 1845 kg/m3. The density of Q is about 2650 kg/m3- with a few assumptions (always a few assumptions) this gives a P value of around 0.7- still quite a lot of porosity in a fired brick. This allows combustion gases (from the dispersed spanish) to escape and gives the brick good drainage characteristics.

Strength

Structure: the essence of a loess/brickearth deposit is structure- the way that the constituent particles are arranged in the ground system. It is the open airfall structure of the deposit which causes the geotechnical problems with loess ground- when loaded and wetted the loess ground structure collapse; hydroconsolidation ensues, subsidence occurs. The metastable nature of the ground causes problems. It also allows easy digging. The man with the spade fares better in loess ground than in ordinary clay-rich ground which can be 'heavy' or 'sticky' and difficult to manipulate. The nature of loess ground means that thick loess deposits can be dug and successfully utilized. Easily dug and easily manipulated- ideal ground for the hand making of bricks; an open internal structure and not too much clay mineral content.

The particulate nature of loess/brickearth underpins all considerations of the development of properties in LS bricks. The ground nature is relatively complex but some chancy generalisations can be attempted. BE is a silty material; assume a mode size of around 30 um- and most of these particles will be quartz. The mode shape of the mode size Q particle can be calculated (with a few necessary assumptions: eg Q is isotropic). There is a probability approach to this problem, or it can be tackled via a very simple Monte Carlo method. If the particle shape is defined by the orthogonal box into which it just fits: the mode shape can be calculated to be about 8-5-2, these are the side ratios. It is a remarkably flat particle- it will eventually determine and dominate the internal structure of the LS brick- and provide its great strength when the particle contacts are emphasized and reinforced. The moulder produces a tight random packing of flattish particles in a cohesive plastic solid.

Dimensions

For a drainage tunnel it is useful to have the surface as smooth as possible- flow should not be impeded in any way. The accurately dimensional LSB allows careful smooth tunnel construction. The nature of BE allows for efficient filling of the brick mould and this ensures good dimensionality and sharp edges-good arris structure.

Chemistry and Mineralogy

The high Q content in the LSB gives it strength and abrasion resistance, and resistance to chemical erosion. The low clay mineral content (of not particularly clayey clays) allows relatively easy melting in the firing sequence. The eutectic in the SiO2-Al2O3 system is close to the silica end of the system; the components in the eutectic system are silica and mullite.

Location and Transportation

The geography is remarkable. The brickearth is on hand or very close to hand. The close to hand brickearth is connected by an efficient transport system directly to the site of the construction activity, and also serves to deliver supplementary fuel to the brick makers. The most significant brick construction in the world is to be emplaced at the heart of the brick universe; hard to imagine a more suitable location- a more apt location.

The problem (of building an extensive sewer system) arose at the centre of a great brick using universe; every fully laden Thames barge coming up from Sittingbourne delivered 50,000 bricks- to be able to use these to build the sewer system and to save the lives of Londoners was an amazing stroke of fortune. The LSB would appear to have been almost ideal for building a large and complex sewer system- so many aspects of its nature pointed to it being well suited to the job in hand.

Choice or chance?  The virtues of London Stock bricks for the construction of the Bazalgette sewer network in Lonfon (c.1860-1880).  Ian Smalley, Arya Assadi-Langroudi, Grenville Lill . British Brick Society Information 148, 10-19, September 2021.

Star Lane & Cherry Orchard Lane: Two brickworks in Essex

 Star Lane brickworks in Essex [TQ 935870]; Cherry Orchard Lane brickworks in Essex [TQ 857898]; south of the River Crouch, near Great Wakering, near Rochford; Brickearth deposits used to make London Stock bricks; among the longer lasting of the Thames Valley brickworks; owned at one time by D.&C. Rutter- who owned brickworks in Crayford. Both sites investigated by Grenville Lill in the 1970s; his TG studies on the London brickearths succeeded and amplified those of Freeman (1964). 

Lill, G.O. 1978.  The nature and distribution of loess in Britain. PhD thesis University of Leeds; etheses. whiterose.ac.uk

London Stock bricks

Alan Cox 1997.  A vital component: Stock bricks in Georgian London.  Construction History 13, 57-66.

The London Stock is a type of brick the manufacture of which is confined to London and south-eastern England (particularly Kent and Essex). It is made from superficial deposits of brickearth (Loess) overlying the London Clay, which are easily worked and produce a durable, generally well-burnt brick. This durability actually increases, since the London Stock brick has the fortuitous advantage of hardening with age and in reaction to the polluted London atmosphere..

Other characteristics of the London Stock result from its method of manufacture, two stages being especially important. The first of these is the practice of mixing the clay with what has been variously known as Spanish, soil, town ash, or rough stuff- that is London's domestic rubbish, which contained a large amount of ash and cinders. The addition of this sifted ash provided a built-in fuel when the bricks were fired..

I.L.Freeman 1964.  Mineralogy of ten British brick clays.  Clay Minerals Bulletin 5, 474-486. 

Sample 63AH; London Stock brick mixture; mainly Pleistocene from Kent.  75% brickearth, 10% estuarine mud, 10% washed chalk, 5% sifted town refuse. The chalk is added to produce the desired yellow colour. Freeman carried out thermogravimetric analysis on his brick clay samples using a Stanton Redcroft TR01 thermobalance.

The TG curve for 63AH suggests not much moisture loess at relatively low temperatures, this would be expected for a material with a relatively low clay mineral content. This is also reflected in the low weight loss at dehydroxylation temperatures. Greater weight loess occurs at higher temperatures where there may be decarbonation reactions from the chalk in the system. 62AK has larger weight losses at moisture loss temperatures and dehydroxylation temperatures indicating a larger clay mineral presence.

This is a very rough first-plotting of the DTG curve for the Freeman sample 63AH- the brickearth mixture. It shows two main thermal events (c.f. the DTA results above); four events can be tentatively identified: A the loss of adsorbed water- not very much water, not strongly held; B combustion of organic material, again not a great reaction, not a lot of organic material present; C clay mineral dehydroxylation, the classic clay mineral reaction, showing a modest amount of clay mineral material in the sample; D carbonate loss CaCO3 >  CaO +  CO2, the added chalk has an effect here, not a huge reaction, only a small % of chalk added. The whole 63AH DTG curve looks quite like the DTG curve for a Canadian quickclay; the dominant quartz of course offers no analytical signal.

For more on DTG applications see: Fordham, C.J., Smalley, I.J.  1983/4 High resolution derivative thermogravimetry of sensitive clays.  Clay Science 6, 73-79. 

Making bricks from Loess

 Large parts of London are made from loess. London grew in the 19th Century; thousands of houses were built with loess bricks- bricks made from the London Basin brickearth. London was well placed with respect to bricks; it could become the great brick-built city. The thousands of houses were all heated by open coal fires which produced vast amounts of ash and cinders- which was collected by 'dust-men' and concentrated into vast dust heaps. This could be sent by sailing barges to the downstream brickworks to be used in the making of the classic Thames 'stock' bricks.

Artist: Edward Henry Dixon 1822-1884.  The cows are grazing near Randall's Tile Yard, York Way (near Kings Cross) London. The triangular structures on the left are tile kilns, a typical tile kiln could be 70 feet high. They can be seen again in the drawing of the Somers Town dust heap (below), and in the York Way panorama.

The brickearth was universal in the Thames valley and there were brick and tile works all over London. Certain brick related locations have become well known via references in diaries and novels and other writings, and by representations by a range of artists. The most famous region is probably that at Battle Bridge, near the current Kings Cross Station, close to the old Smallpox Hospital (which appears in several E.H.Dixon pictures); close to Somers Town, at the southern end of York Way.

Signed EHD 1835. That is York Way; just off the bottom of the picture is the Regents Park Canal.

Charles Dickens last full length novel, Our Mutual Friend 1865, features a dust heap- the novel is based on the article 'Dust; or ugliness redeemed' by R.H.Horne 1850, which appeared in the journal Household Words (published by Dickens). The site of the Smallpox Hospital is now occupied by St.Pancras Station, adjacent to the British Library and Kings Cross Station and the Francis Crick Institute.  Nicodemus Boffin, the most agreeable character in Our Mutual Friend, lived near the great dust heap at Battle Bridge.

The building with the small dome is the Smallpox Hospital. This is the Great Dust Heap at Somers Town; this is the dust heap that was sold to Russia in 1848 for £40 000 to assist in the rebuilding of Moscow. Top right can be seen tileyard structures; local brick materials being produced.

This is Mr Boffin, his fortune is based on dust, his passion is for books. "Where I live, said Mr Boffin, is called The Bower.. up Maiden Lane, Battle Bridge, ask for Harmony Jail, and you'll be put right.."

Wegg looked into an enclosed space where certain tall dark mounds rose against the sky..."

E.H.Dixon 1837 appears to have produced two versions of this picture- of the great dust heap. This is the 'dark' version. Note the cloud of dust being raised by carpet beating. The other version, the 'light' version is reproduced in the previous blog. These dust heaps provided subsistence for a whole variety of people, who sorted the mixed materials into various useful sub-classes. R.H.Horne 1850 wrote of..

"..  the next sort of cinders, called the breeze because it is left after the wind has blown the finer cinders through an upright sieve, is sold to the brickmakers. "

For an excellent discussion of dust heaps and the story of the dust heap being sold to Russia see:

Cox,A., Hounsell, P., Kempsey,S., Kennett,D.H., Worthy, S. 2017.  London's dust mountains and bricks to rebuild Moscow after 1812.  British Brick Society Information 137, 9-34.

Questions about Brickearth

Two sets of questions: 1 historical & 2 scientific. Quite a lot of explanation required. The brickearth being considered is the brickearth found in south east England, particularly in south Essex and north Kent. This is what we now think of as brickearth. The Oxford English Dictionary OED (which will be our main etymological source) has a geological definition for brickearth/ brick earth:

brick earth n.  Earth or clay suitable for making bricks. Now chiefly in form brickearth. A fine grained silty deposit consisting of or derived from loess, occurring in the Thames basin and other parts of southern England. 

1816 W.Smith. Strata identified 11.  The Oak-tree clay also may be mistaken or confounded with the Brick earth, which in several parts produces good oak.

The famous early reference to brick-earth is that by John Evelyn the diarist, who in 1667 is involved in schemes to rebuild post-fire London in brick.

6 March 1667: I proposed to my Lord Chancellor, Monsieur Kiviet's undertaking to wharf the whole river of Thames, or quay, from the Temple to the Thames, as far as the fire destroyed, with brick, without piles, both lasting and ornamental.

26 March 1667: This afternoon I had audience of his Majesty, concerning the proposal I had made of building the quay...  Sir John Kiviet dined with me. We went to search for brick-earth, in order to a great undertaking. 

7 Sept.1667: Came Sir John Kiviet, to article with me about his brickwork.

2 April 1668: To the Royal Society, where I subscribed 50,000 bricks, towards building a college.

Evelyn lived in Deptford, on the south bank of the Thames, adjacent to Deptford Creek. He lived at Saye's Court, Deptford and it appears that he may have been planning to use local ground for his bricks.

14 Aug. 1668.  His Majesty was pleased to grant me a lease of a slip of ground out of Brick Close, to enlarge my fore-court, for which I now gave him thanks.

Actually the Evelyn brickmaking project does not go well (one suspects that Sir John Kiviet may have been less than trust-worthy) and another famous diarist comments on the endeavour:

Samuel Pepys 23 Sept 1668: At noon comes Mr Evelyn to me, about some business with the office, and there in discourse  tells me of his loss, to the value of £500, which he hath met with, in a late attempt of making of bricks upon an adventure with others, by which he presumed to have got a great deal of money; so that I see the most ingenious men may sometimes be mistaken. 

After the Great Fire of London there was a huge increase in brick production because it was ordered that London should be rebuilt from non-combustible materials. The Company of Tylers and Bricklayers had kept some control on the world of bricks but this proved impossible to maintain after the fire and widespread brick manufacture developed. And, of course, the fates had placed, in the Thames basin, a large amount of loess material (to become eventually known as brickearth) which could be turned into excellent bricks- assisted by a great post-fire discovery.  

Useful reference: T.P.Smith 2007. 'Upon an adventure with others' John Evelyn and brickmaking after the Great Fire of London. British Brick Society Information 103, 10-15.

According to the Company of Tylers and Bricklayers in 1714 it was not until after the failure of the Evelyn Deptford brickyard that a new method of brick masking was discovered.. Here one of our questions might be answered. When was it discovered that adding rubbish to the brickclay made brickmaking in Kent & Essex extra profitable? A virtuous network was established with a great and expanding city needing an endless supply of bricks connected by a convenient river to large deposits of ground material which proved ideal for brick making. And the city waste provided fuel for firing the bricks and enabled the transport barges to be loaded in both directions of travel. The discovery of the useful combustible admixture appears to have been made by accident.

" the practice of using ashes commonly called spanish (was) begun about forty years since [hence not until early 1670s] occasioned by diging up several fields contiguous to the city after the great fire which fields having been much dunged with ashes it was observed the bricks made with earth in those fields would be sufficiently burned with one half of the coles  commonly used. "

Why was the admixture called Spanish?  Here is one of the great brickearth questions. Loessic brickearth + Spanish makes fine bricks; but why is Spanish so-called?  And have our investigations exposed an error in the OED? 

OED 1714 London Gazette no.5209/4.  Together with two stools of Brick-Earth ready dug and spanished.

OED definition: etymology- of obscure origin; obsolete, rare. Earth or clay unfit for brickmaking.

This definition is wrong; it should read- rubbish or waste material added to brickearth to improve the efficiency of the firing process. OED suggests that Spanish is a bad thing but the opposite is true. Spanish is useful and virtuous in brickmaking with Thames brickearths (aka loess).

Daniel Defoe (yet another journal keeper of the time ; see in particular Journal of A Plague Year- not 2020 but 1665) casts a useful light on Spanish.

Daniel Defoe:  A brickmaker being hired by a Brewer to make some bricks for him at his country house, wrote to the brewer that he could not go forward unless he had two or three loads of Spanish, and that otherwise his bricks would cost him six or seven chaldrons of coals extraordinary, and the bricks would not be so good and hard neither by a great deal, when they were burnt

There ensues some misunderstanding because the brewer understands spanish to be liquorice juice.

Defoe was writing in 'The Complete English Tradesman'(1726) and he was making a point about clarity in communication. Chaldron was a volume measure, maybe about 32-36 bushels; Newcastle coal about 2850-2978 lbs; 1.309 cubic metres..

Defoe again:  the brickmakers all about London, do mix sea-coal ashes, or laystal-stuff, as we call it, with the clay of which they make bricks, and by that shift save eight chaldrons of coals out of eleven, in proportion to what other people use to burn them with, and these ashes they call spanish.

Laystal: a place where rubbish and dung are deposited. 

OED 1725 Act 12 Geo I c.35.  Several persons.. continue to make bricks of bad stuff and unsizeable dimensions, and do not well burn the same, and in making thereof mix greate quantities of soil called Spanish.  In other words too much Spanish and not enough brickearth, but the spanish properly used is a valuable ingredient. Spanish begins to be used after the great fire and contributes to the exploitation of the great brickearth deposits of Kent and Essex. And they were great deposits- hidden by history and industry were very large deposits of loess material which was used in the construction of a large brick city. Eventually brickearth will come to mean the deposits in Kent and Essex, and the loessic brickearth will come to be differentiated from brick clay in general.

The Smeed Dean brickworks in Kent was said to be the largest in the world; 60 million bricks were made in 1877. The loess deposits being exploited were of considerable size and thickness but because they had largely been mined away before loess science developed tended to be somewhat neglected and under-appreciated. These bricks were made with the aid of the added ashes and cinders, the spanish, and the history of the spanish could be a topic for further exploration. The ashes and cinders from houses all over London were collected into vast heaps and accumulations, and the trade in these materialsdependent on the brick making industry, provided a source of much economic activity. 

The last complete book by Charles Dickens, Our Mutual Friend 1865, relates largely to a large heap of spanish which serves to provide the monetary fortune for some of the protagonists. The picture by E.H.Dixon 1837 shows a large dust heap in the Kings Cross area.

 

Useful reference: Richard Hernry Horne 1850. Dust or ugliness redeemed.  Household words 1, 379-384.  The brickmakers at Uxbridge would contract for 15 or 16 thousand chalrdons of cinder-dust.. Brickmakers all around London relied on the constant supply of spanish and on the vast resources provided by the brickearth deposits.

Another dust heap picture; this time by C.H.Matthews

Questions 2: scientific

Where did all that brickearth/loess come from, and how was it emplaced? It appears that the story of the English loess is complicated and involves many steps and events.

The chart shows the route to the bricks. The chart (constructed by Colin Bunce) shows events and stages on the journey from the initial loess particles to the bricks made by Smeed Dean. It follows the old PTD (1966) scheme and indicates formation events, transportation events and deposition events (hence P, T and D). The D2 event puts loess all over SE England; subsequent events move this material about to give the deposits and concentrations that we observe. The large drainage basin is the Thames basin and material falling therein is eventually concentrated in the Kent and Essex brickearths. The Kent brickearth is augmented by material from the Medway basin.

Loess material in SE England; it has been suggested that it is the concentration of loess material in SE England that accounts for the concentration of brick buildings in SE England.

Useful reference: Smalley, I.J. 1986.  The nature of brickearth and the location of early brick buildings in England.  British Brick Society Information 41, 4-11.

William Whitaker in Plumstead (1889)

Whitaker, W.  1889.  The Geology of London and of Part of the Thames Valley (Explanation of Sheets 1, 2 and 3).  Memoirs of the Geological Survey. England and Wales vol.1 Descriptive Geology. London HMSO 556p.

On p.432 WW is in Plumstead in S.E.London (close to Erith and Crayford- the great depositories of brickearth aka loess).  He provides a sketch by 'my collegue Mr.Goodchild' showing brickearth in Plumstead.
This is the Goodchild sketch, redrawn and thus scale is meaningless but top to bottom of picture is about 20 feet (6m). details below

a. Loamy brickearth

b.  More clayey brickearth

c.  Broken up chalk

d.  undisturbed chalk

Loess Letter: the story of an INQUA newsletter

This is the story of Loess Letter, an INQUA newsletter which started life at the DSIR Soil Bureau in New Zealand in 1979 and was replaced in the new electronic world by the Loess Ground blog in 2015.  It is a story of adventure and romance- no its not its a tale of obsessive bibliography and the evolution of loessic studies at an interesting time in the development of Quaternary Research. Loess Letter has an ISSN number 0110-7658 and all the issues are available online at www.loessletter.msu.edu. Large efforts by Dr.Randall Schaetzl and dedicated helpers at Michigan State University have ensured online access to the complete oeuvre.

cover concatenation by Balazs Bradak

Its a tale of several parts; start at the NZ Soil Bureau in 1979; a newsletter for the Western Pacific Working Group of the INQUA Loess Commission. Issues 1-7 were produced by the Soil Bureau, printed by the NZ Government Printer in Wellington and distributed by the Bureau (1979-1982). Then a move to Canada, to the University of Waterloo in Ontario. Issues 8-16 from Waterloo, supported by NSERC (1982-1986). Then to the University of Leicester; issues 17-34, some initial support from the Royal Society (1987-1995). Issues  35-65 were produced at Nottingham Trent University (1996-2011, a mighty effort by NTU), and then the final sequence 66-72 back to Leicester University. The whole sequence was published online by Michigan State University and all issues can be accessed via www.loessletter.msu.edu. The transitions were 7 Ap 82 > 8 Oc 82; 16 Oc 86 > 17 Ap 87; 34 Oc95 > 35 Ap 96; 65 Ap 11 > 66 Oc 11; 72 Oc 14.

Loess Letter 1-10 was published as a compilation by Elsevier Geobooks in Norwich; ISBN 0 86094 218 X 1987. Very few copies were printed; if you come across a copy in your local second hand bookshop it will be a surprise (it may not be valued now as a rare book- but in the future: who knows?). OCLC only lists one copy in a library: in Technische Informationsbibliothek (TIB) Hannover 30167 Germany.

               title by Liu Tungsheng written at NZ Soil Bureau 1980

Supplements. A series of supplements was produced and given limited circulation. The supplements were initially produced as a contribution from the Loess Commission to the 12th INQUA Congress held in Ottawa in 1984. It was an erratic series of items, a few of which may have lasting value. A translation of the Pyaskovskii paper on deep soil formation which was produced at the Soil Bureau was eventually published as LLS 3, and in view of its significance again as LL72. The LL72 republication means that it is readily available online. Professor Edward Debyshire's inaugural lecture in the Geography Department at Leicester University on 28 April 1987 was published as LLS 21.
The most ambitious supplement, the most ambitious item in LL publishing history, was the reissue of John Hardcastles's Notes on the Geology of South Canterbury; originally published in 1908 by the Timaru Herald and republished, with editorial apparatus and maps, by LL in 2014 . The Hardcastle supplement was well circulated in NZ and reached a goodly distribution of universities and institutions (with assistance from the South Canterbury Museum).

The Supplements
1.  Loess & Agriculture. Kwong & Smalley. Oct.1983
2.  Dust mantles in Australia. A.J.Dare-Edwards
3.  B.V.Pyaskovskii, Loess as a deep-soil formation.  July 1989.
4.  The loess formation in Bulgaria
5.  The hydrogeology of loess 1883-1982
6.  Loess in Pleistocene soils on Mount Kenya. W.C.Mahaney
7.  Geotechnical investigations of loess in the USA. Alan Lutenegger et al.
8.  Lyell on Loess. A section from Principles of Geology 4th ed.1835
9.  Dokuchaev and the Russian approach
10. Kriger. A section from Kriger 1965 (in Russian)
11. Obruchev. A translation of the Obruchev article in Novi Mir- a popular account of loess
12. The Quaternary of the Great Hungarian Plain
13. Kriger again. This is the bibliography from Kriger 1965- the most important Cyrillic loess     bibliography available, critical for the study of historical Russian loess investigations.

14. Yeliseyev 1973 translated
15. Vaskovsky
16. Tutkovskii sampler
17. Kondratov's Arctic Lands
18. M.P.Lysenko
19. Pelisek
20. Seventy Books on Loess: March 1991
21. E.Derbyshire. The skin of the Earth and the way of the World
22. E.Derbyshire. Loess and the Argentinian Pampa.
23. John Hardcastle. 100 years of loess stratigraphy.

Hardcastle. Hardcastle as the pioneer of loess stratigraphy. John Hardcastle of Timaru as a significant pioneer of Quaternary Studies. LL supported JH- his bibliographical uncovering coincided exactly with the launch of the Western Pacific Working Group and his visibility has increased as loess stratigraphy has grown in extent and achievement. Supplement 23 was published for the 13th INQUA Congress in Beijing in 1991 and its widespread circulation placed JH nicely into a proper niche in geohistory. Supplement ns2 was published for the 19th Congress in Nagoya Japan in 2015-this was the climax of the LL/JH project- a republishing of his book Notes on the Geology of South Canterbury.