25 April 2022

The ‘Iron Trunk’ is a feat
of Georgian engineering
high above the Great Ouse

Crossing the ‘Iron Trunk’ Aqueduct above the River Great Ouse, on the edges of Buckinghamshire and Northamptonshire (Photograph: Patrick Comerford, 2022)

Patrick Comerford

On a walk in the warm sunshine last week through the countryside on the edges of Buckinghamshire and Northamptonshire, two of us crossed the ‘Iron Trunk’ Aqueduct, also known as Cosgrove Aqueduct, between Wolverton and Cosgrove.

This navigable cast iron trough aqueduct outside Milton Keynes is a magnificent piece of Georgian engineering and is the world’s first wide canal cast iron trough aqueduct. It is more than 200 years old and it carries the Grand Union Canal, once an important trading route between London and the Midlands, over the River Great Ouse.

The aqueduct is formed of two cast iron trough spans, with a single central masonry pier. The abutments were also built in masonry but were re-faced in brick in the 20th century. The trough is 4.6 metres wide, 2 metres deep and 31 metres long. The canal surface is some 12 metres above the surface of the river, and the approach earthworks total 800 metres.

To cross the course of the River Great Ouse, the lowest point between the summits at Tring and Braunston, flights of locks were constructed for the Grand Junction Canal, later absorbed by the Grand Union Canal in 1800. Four flights were built at the south-east and five at the north-west, allowing the canal to descend to cross the river on the level.

The company engineer, William Jessop (1745-1814), is also known for his first major work, the Grand Canal of Ireland. Jessop designed a three-arch brick viaduct so that the Grand Union could cross the Great Ouse at a higher level, reducing the water loss and delay in locking down to river level.

Thesurface of the River Great Ouse is 12 metres below the aqueduct (Photograph: Patrick Comerford, 2022)

The structure was opened in 1805, but a section of the canal embankment soon collapsed. After repairs, the aqueduct structure itself collapsed in February 1808, severing the canal.

Jessop is sometimes blamed for the failure of the first structure, but the collapse actually led to a legal dispute with the original contractor. The dispute went to trial, and damages were awarded to the Grand Junction Company for the loss of trade while the canal was out of use, and the cost of replacing the aqueduct.

Another company engineer, Benjamin Bevan, began designing a replacement structure, and the original lock system was quickly reinstated.

By then, Thomas Telford had successfully built cast iron trough aqueducts at Pontcysyllte and at other places. Bevan decided to take forward the technology by designing the world’s first wide canal cast iron trough. The structure was cast at the Ketley foundry at Coalbrookdale which had produced the Longdon-on-Tern aqueduct for Telford.

The components were taken to Cosgrove by the canal itself. They were assembled and erected on the site, and the new structure was completed in January 1811. Bevan designed the floor sections to be arched, providing the additional strength needed to resist the substantial additional loading of a wide canal. The arch ribs are integral to the side plates of the trough and give additional shear strength.

The towpath is cantilevered from one side and are supported by diagonal struts. There is a cattle creep in the embankment on either side of the main structure to provide field-to-field access for cattle.

The aqueduct was refurbished in 2011 to celebrate its bicentenary. Today, the ‘Iron Trunk’ aqueduct and its towpath provide a popular cycling route and this is a breath-taking location to relax and watch the canal boats and to relax in some quiet and calm moments.

After crossing the aqueduct, two of us continued on to Cosgrove, where we had lunch in the April sunshine in the Barley Mow before returning to Stony Stratford.

A Constable-like scene on the canal at Cosgrove, close to the ‘Iron Trunk’ aqueduct (Photograph: Patrick Comerford)

Praying with the Psalms in Easter:
25 April 2022 (Psalm 61)

‘Lead me to the rock that is higher than I; for you are my refuge’ (Psalm 61: 2-3) … the rocks above the beach at Foinikas on the south coast of Crete (Photograph: Patrick Comerford)

Patrick Comerford

During this season of Easter, I have returned to my morning reflections on the Psalms, and in this Prayer Diary on my blog each morning I am reflecting in these ways:

1, Short reflections on a psalm or psalms;

2, reading the psalm or psalms;

3, a prayer from the USPG prayer diary.

Psalm 61:

Psalm 61 is to be played on a neginah or stringed instrument. In the slightly different numbering system in the Greek Septuagint and Latin Vulgate this is Psalm 60.

This Psalm is attributed to King David and is called in Latin Exaudi Deus (‘Hear my cry, O God’).

The Jerusalem Bible calls it a ‘prayer of an exile.’ It describes verses 1-5 as the lament of an exiled Levite, and verses 6-7 as a prayer for the king.

The Czech composer Antonín Dvořák set verses 1, 3 and 4 to music, together with part of Psalm 63, in No. 6 of his Biblical Songs (1894).

‘You are my refuge, a strong tower against the enemy’ (Psalm 61: 3) … the Wignacourt Tower in Saint Paul’s Bay, Malta (Photograph: Patrick Comerford, 2022)

Psalm 61 (NRSVA):

To the leader: with stringed instruments. Of David.

1 Hear my cry, O God;
listen to my prayer.
2 From the end of the earth I call to you,
when my heart is faint.

Lead me to the rock
that is higher than I;
3 for you are my refuge,
a strong tower against the enemy.

4 Let me abide in your tent for ever,
find refuge under the shelter of your wings.
5 For you, O God, have heard my vows;
you have given me the heritage of those who fear your name.

6 Prolong the life of the king;
may his years endure to all generations!
7 May he be enthroned for ever before God;
appoint steadfast love and faithfulness to watch over him!

8 So I will always sing praises to your name,
as I pay my vows day after day.

Today’s Prayer:

The theme in this week’s prayer diary of the Anglican mission agency USPG (United Society Partners in the Gospel) is ‘Logging in the Solomon Islands,’ and was introduced yesterday morning by Brother Christopher John SSF, Minister General of the Society of Saint Francis.

The USPG Prayer Diary this morning (25 April 2022, Saint Mark the Evangelist) invites us to pray:

We give thanks for the life of Saint Mark the Evangelist. May we devote our lives to evangelism and witness..

Yesterday’s reflection

Continued tomorrow

A figure representing Saint Mark at the base of the memorial cross in the churchyard at All Saints’ Church, Calverton … the Church Calendar today commemorates Saint Mark the Evangelist (Photograph: Patrick Comerford, 2022)

Scripture quotations are from the New Revised Standard Version Bible: Anglicised Edition copyright © 1989, 1995, National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org