timeline item
Results
Here is the information we have
on the item you selected
More like this
NEW SEARCH
| |
sign up for our newsletter
© 2017 Engineering Timelines
engineering-timelines@severalworld.co.uk
engineering timelines
explore ... how   explore ... why   explore ... where   explore ... who  
home  •  NEWS  •  search  •  FAQs  •  references  •  about  •  sponsors + links
Eddystone Lighthouse, Smeaton Tower (relocated)
Plymouth Hoe, Devon, UK
Eddystone Lighthouse, Smeaton Tower (relocated)
associated engineer
John Smeaton
date  12th June 1757 - 16th October 1759 (reloc. 1884)
era  Georgian  |  category  Lighthouse  |  reference  SX476538
ICE reference number  HEW 73
photo  Smiles
John Smeaton's celebrated and influential stone lighthouse was originally sited out to sea on Eddystone Rocks, 22.5km south of Plymouth. It was dismantled in 1882 and re-erected at Plymouth Hoe in 1884 by William Tregarthen Douglass, son of eminent engineer and builder of the present lighthouse, Sir James Douglass.
Two lighthouses preceded Smeaton's tower. The first was built on House Rock in 1696-98 by the engraver Henry Winstanley (1644-1703) and came down in a tempest in November 1703, killing Winstanley himself. The second tower was erected by silk merchant John Rudyerd in 1708-9. Both were largely made of timber with granite ballast. The idea was that timber would move under wave action rather than resist it.
Rudyerd's lighthouse was destroyed by fire on 2nd December 1755. Smeaton was recommended for the job of rebuilding it by the then President of the Royal Society, even though his civil engineering career had barely begun. It was to be a turning point for him.
Smeaton was the first 'engineer' to consider the problem of constructing a lighthouse at sea, and decided to build entirely in stone. He took the shape of an oak tree as his inspiration — a large heavy base rooted in the soil with a curved tapering pillar above, keeping the centre of gravity low. The outer surface was to be as smooth as possible to deflect the waves. The interlocking stones of London pavements gave him the idea of dovetailing the substructure stones with the living bedrock.
He decided that all the stone exposed to the sea was to be Cornish granite, with interior masonry of Portland stone. The blocks were jointed with a lime/pozzolana mortar that set in wet conditions, invented by Smeaton himself. The tower was almost 22m high and some 7.6m in diameter at the base.
Once the substructure was complete in August 1758, progress was rapid and the final lintel stone at the top of the tower was laid on 24th August 1759. The octagonal iron lantern with its copper cupola roof (hoisted in one piece) was fitted in September. The 24-candle light was first lit on 16th October.
The upper, hollow part of the tower contains four chambers, one above the other, for stores and the keepers. At each floor level, an endless iron chain was set into a groove in the outer wall and molten lead poured over it. Smeaton had read about Sir Christopher Wren's design for the cupola of St Paul's Cathedral, where an endless chain contains the thrust of the dome, and decided to use this idea for extra safety.
Smeaton's tower was built by a group called the Proprietors of the Lighthouse, who leased the site from Trinity House (the overseer of lighthouses in England and Wales). In 1807, the lease expired and ownership reverted to Trinity House. Three years later the candles were replaced by oil-fired catotropic reflectors (1,020 candela).
Robert Stephenson, the Scottish lighthouse engineer, reported in 1818 that the cave in the rock beneath the tower and lack of strength of the rock itself could endanger the structure. The keeper reported that the tower moved in heavy seas, and waves would engulf the light. Remedial work was carried out in 1838. Iron straps were set into the masonry of the interior walls, tying the rooms together. The curved cornice below the lantern was trimmed flush to reduce wave impact on the column.
In 1845, the iron lantern was replaced with a larger bronze one, and the lamp replaced with a Fresnel revolving diopteric lens (3,280 candela). The lighthouse's exterior was painted for the first time in 1861. It was white at first, then the more familiar red and white hoops were done in 1875.
Further worries about the rock in 1877 lead to the decision to build a new lighthouse. Work began the following year under Sir James Douglass, 40m south-east of House Rock. It was completed in 1882 and Smeaton's tower went dark on 3rd February, followed by decommissioning and dismantlement. In 1884, the top 28 courses and lantern were rebuilt at public expense on Plymouth Hoe — on the site of Sir Francis Drake's famous beacon.
The reconstruction used Portland cement mortar instead of lime mortar and the tower began to suffer from problems with damp. Restoration work was carried out between 1999 and 2001, and the tower is again open to the public.
Smeaton's tower was an astonishing acheivement, built as it was on a small area of rock only accessible at low tide in the summer months, using manpower alone, some 40 years before battery-powered electricity. It's design continued to be emulated for some 150 years.
Resident engineer (1756-9): Josias Jessop
Resident engineer (1882): William Douglass
Research: ECPK
bibliography
"A narrative of the building and a description of the construction of the Edystone lighthouse with stone: to which is subjoined, an appendix, giving some account of the lighthouse on the Spurn Point, built upon a sand"
by John Smeaton, G. Nicol, London, 1793
"Smeaton's Tower" by Christopher Severn
Seafarer Books, Woodbridge, 2005
www.trinityhouse.co.uk
reference sources   CEH SouthJS
Location

Eddystone Lighthouse, Smeaton Tower (relocated)