Thursday 20 December 2012

Information wanted on a Wheatstone Bridge

We received the following email from one of our followers:

" I am seeking information about a Wheatstone Bridge set that belonged to my father-in-law’s father who was an electrical engineer for the LNER in the early 1900’s and worked in Hartlepool.  He used for his work and it must be around 90 years old I would have thought.  I see that is made by Siemens Brothers and believe that they were based/had factories in Greenwich and Hartlepool'.

and he attached some pictures - which are shown below.

So  - we got in touch with the experts - with the Siemens Brothers Engineering Society - and here is their reply:

"I have been in touch with some of my colleagues in the Siemens Brothers Engineering Society and have undertaken some research myself. There is plenty of information on internet search engines so I have given below a general summary and have tried not to get too technical.
A Wheatstone Bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. [The bridge is formed of resistors connected in a diamond-shaped pattern] Typical applications were: measuring the resistance of a length of cable. For the LNER this could well be railway signaling cable or for Siemens Brothers, telephone cables.
Curiously the Wheatstone Bridge was not invented by Sir Charles Wheatstone (1802 - 1875), but by Samuel Hunter Christie in 1833, but was improved and popularised by Wheatstone in 1843, when he gave full credit to Christie. The Wheatstone Bridge uses the concept of a difference measurement, which can be extremely accurate. Variations of the Wheatstone Bridge can be used to measure capacitance, inductance and impedance. The significance of measuring the 'unknown' resistance can thus be related to the impact of some physical phenomenon such as force, temperature, pressure etc. In practical terms a 'break' in a cable.
The most common use of the Wheatstone Bridge in day to day telephony and telegraphy was thus the location of cable faults. By determining the resistance of a fault and comparing it with a pre-determined map, it was possible to send repairmen out to the exact location of a fault, accurate to within a few feet.  Brass plugs (as seen in the picture) were used to throw resistance in and out of the circuit until a balance was achieved as indicated by zero deflection and thus zero current flow through the galvanometer mounted in the centre of the instrument, again as seen in the picture..
The Wheatstone Bridge was further developed by Kelvin to form the Kelvin Bridge , the concept being further extended to alternating current measurement by James Clerk Maxwell in 1865.
Various formats of the Wheatstone Bridge were thus developed and manufactured by specialist companies. We do not have any specifics on the particular model that belonged to Mr Kennnedy's father in law's, father. Clearly it was made by Siemens Brothers & Co. Ltd., London, at the main Woolwich Works. It would have been made and in use in the late 19th century and the earlier part of the 20th century for typically resistance measuring and fault finding on cables as described above. The instrument could therefore be about 100 years old. By a strange coincidence Samuel Hunter Christie worked at the Royal Military Academy in Woolwich. Siemens Brothers did have several satellite factories including one in Hartlepool. It is unlikely that the instrument would have been sourced via Hartlepool as we believe this factory came on stream after the 1939/45 war.
A Wheatstone Bridge would of little 'practical' use to todays telephone collector. However in good condition it would form a most attractive part of any collection and could be of interest to a Science Museum [who may also be able to put a value on it] or a Heritage Centre. The Siemens Brothers Engineering Society has donated a great many items to the Greenwich Heritage Centre, which is actually located in Woolwich. If any further information is required please contact me.
Brian Middlemiss
On behalf of the Siemens Brothers Engineering Society.



Sunday 16 December 2012

In August this blog reproduced an article by Dr.Robert Carr originally published in Industrial Archaeology News about London Bridge Station. That article achieved the highest number of views of any article this blog has published. Here is his next article from the current issue of the same publication.

A large London railway terminus is to be completely demolished to divert two railway tracks through the site. Known to relatively few people, the Brighton part of London Bridge Station appears doomed. This raises familiar issues concerning the different treatment of architecture and engineering as well as those concerning World Heritage Sites.
(see Industrial Archaeology News 162 pp 8&9

The London and South Coast Railway’s terminus at London Bridge station has long been something of a Cinderella station. The main problem is that relatively few people are familiar with it. Most passengers who use London Bridge only remember the through platforms to the north where conditions can be really dreadful. Redevelopment here is sorely needed. The London Bridge terminus lacks glamour in that the trains only go to relatively humble destinations in the South East. There never was a Golden Arrow or Night Ferry to Paris as at Victoria, or a Cornish Riviera Express to Penzance departing from Paddington.

It is not really clear why it is necessary to demolish the whole of the 1864-7 terminus roof just to re-route two railway lines through it. An entry at the northwest corner facilitated by a beam supported on columns should be within the bounds of present day structural engineering. About a hundred or so years ago this kind of rearrangement was undertaken at railway stations such as Rugby and Crewe and a good example can still be seen at Chester General Station. There may, however, be other reasons not readily apparent but these have not been made clear. One difference is that at London Bridge the station is not at ground level. The whole edifice is supported on substantial brick arches.

However when one considers that, under Nick Derbyshire in 1985-92, Liverpool Street station was rebuilt and extended in a matching Vicwardian style, what would be needed at London Bridge seems modest. City money was involved then and Southwark is relatively impoverished. But attitudes change. About forty- four years ago it was seriously intended to demolish St Pancras station and its listing by Lord Kennet was highly controversial. Many people then considered St Pancras a hideous Victorian monstrosity. At London Bridge we are now having a re-run of the nineteen sixties. The enlightenment of recent years may be coming to an end.

Rather than just separate covers for each island platform as presently proposed, a less unfortunate solution for the station might be a great overall roof, perhaps something like that by Cesar Pelli for the Docklands Light Railway at Canary Wharf. A splendid new roof, say something like the great arch Richard Rogers proposed for the combined King's Cross and St Pancras stations, would really put the London Bridge station on the map and could commensurate in scale with the Shard tower which is intended to be the nucleus for a cluster of tower blocks, as number one Canada Square was for the redevelopment of the Isle of Dogs.

However, objections from the United Nations' cultural organization UNESCO regarding sight lines for World Heritage Sites might prevent further high rise building in the London Bridge area going ahead. Last December a monitoring mission reported that the visual integrity of the Tower of London had been compromised by the building of the Shard tower, the tallest completed building in Europe at 1,016 feet high, and advised that further towers would compound the problem. Similar considerations also apply to redevelopment near Waterloo station which is likely to involve the demolition of Elizabeth Tower, Elizabeth House and some other buildings.

Once granted, World Heritage Site status is not guaranteed in perpetuity and can be removed if unsympathetic redevelopment takes place. In 2004 UNESCO declared the Elbe Valley at Dresden a World Heritage Site. A twelve-mile stretch of landscape, this included the city centre and baroque palaces, churches, opera house, museums. However, after first being placed on list of endangered sites in 2006, the historic area of the city lost its title in June 2009 for the wilful breach of the UNESCO World Heritage Convention. This was due to the construction - the WaldschliiBchenbrucke - a conspicuous composite-steel four-lane motorway bridge across the valley less than two kilometres from the historic city centre.

Dresden is only the second World Heritage Site ever to be removed from the register. UNESCO made clear in 2006 that the bridge would destroy the cultural landscape if building went ahead. Legal moves by Dresden City Council to prevent the bridge from being constructed were unsuccessful.

The WaldschliiBchenbrucke is obtrusive - a massive bowstring-like construction which externally resembles concrete. Could they not have built a low rise bridge similar to some of the nearby Elbe crossings? The river here is not navigable by seagoing ships which need substantial headroom. This really does look like a wilful violation of the UNESCO convention.

All this may mean that in London the continued redevelopment of the London Bridge area would be inhibited and the station itself left in rather a dreadful mess following implementation of the low-rise low-cost scheme presently proposed for it. Surely this was just an interim proposal to cover the period until sufficient funds become available to build an appropriate new station? The simple wavy-roof platform covers presently envisaged are hardly great architecture and certainly not imposing. London Bridge station looks like being further demeaned. It should be borne in mind that curved glass panels are extremely difficult to keep clean. This maintenance problem was soon discovered at Waterloo Eurostar station, opened in November 1994.

Considering now the South Eastern Railway offices these have recently been cleaned so perhaps they will be retained after all. The controversy over the demolition of these offices has served as a red herring, deflecting public attention away from the proposed demolition of the terminus that is relatively hidden away and less well known to the public. The suspicious might suggest a conspiracy but it is all too easy to jump to incorrect conclusions. A crude interpretation in base human terms is generally insufficient to account for the chaotic way in which the world behaves. Such matters are complex and essentially incomprehensible. If something happens there are not necessarily a reason, let alone a human being to blame.

Returning to the issue of the ironwork of the terminus roof. there is now some suggestion that it might be put in store for future re-use. This is an attractive proposition. At least it might be possible to save the longitudinal crescent roof. If this were re-erected at a greater height than at present, the effect could be magnificent. However, at Greenwich the excellent wrought iron roof of the Neptune Hall of 1873-4, a former gymnasium designed by Sir Andrew Clarke RE, was put in store with the intention that it would soon be re-erected. After fifteen years nothing has happened and such things once dismantled and stored have a tendency to get lost, piece by piece, until reuse becomes impossible.

The situation at London Bridge station is fairly typical. The unlisted architecture of the 1897-1900 South Eastern Railway offices has overridden in importance the listed 1864-7 engineering of the railway terminus roof. Once more is it being demonstrated that the architect is more important than the engineer? It should be noted, however, that the architect who worked on the station with the engineer F D Banister was C H Driver (1832-1900). Driver was responsible for many considerable works and was probably the architect for Crossness pumping station, 1859-65. The main buildings there were listed grade I in 1980.

On a sunny day a visit to the LBSCR terminus in the quiet of the afternoon can be recommended. It is easy to appreciate the merits and shortcomings of the building then. Presently, this part of the station might be a little underused but the routing of twin Thameslink tracks through the northern part would rectify this and, if the terminus could ever be redeveloped a la Liverpool Street, a wonderful station worthy of a great new business quarter to rival Broadgate might be achieved.

Dr. Robert Carr.
Industrial Archaeology News. No. 163 Winter 2012. Pp 10-11.
Published Association for Industrial Archaeology

Thursday 6 December 2012

What do we know about windmills

We have a note from Rob who is 'currently in the process of completing a fairly hefty tome on the > windmills of SE London and NW Kent, concentrating on sites from the old  London border of Kent to the Darent valley.'
He is asking GIHS if we can help with the following

a windmill attached to a water-powered paper mill, described as 'near the East India Docks in Deptford', insured by a gentleman called Josiah Johannott (apparently a papermaker from Switzerland) in > 1751. Mr Johannot was declared bankrupt shortly afterwards and the > mills were advertised for sale in the London Gazette in 1754
 "To be Sold to the highest bidder, pursuant to an Order of the Lord High Chancellor in a Commission of Bankrupt awarded against Josias Johannot, late of Deptford, Paper Maker, on 25 February inst. at the Guildhall, London.
A leasehold estate of which there are ninety years to come from Christmas last, consisting of a water-mill, and Windmill, used for the  making of Paper; a dwelling house, garden and wharf, two small tenements and Yards adjoining to the Mill, the whole containing, in Front next the River Thames, 200 feet or thereabouts, adjoining to Wells's Dock. Also meadow land adjoining, situate at Deptford.   Likewise the Utensils in and about the said Mills for making of Paper."

Rob says he cannot place this mill at all, and it  appears to be unrecognised in historical research. A wind powered paper mill in the UK is very rare, and I have no records for a watermill either; in fact this could be a tide paper mill, again a first. Any thoughts? My guess is that it was somewhere in the  Victualling Yard, but I am baffled.

Victualling Yard mills. I have a succession of windmills in the Victualling Yard at the end of the now gone Windmill Lane. The government appear to spend enormous amount of money on these, in order  to supply ships biscuits to the fleet. They seem to be burned down or sold off at some regularity. The last one I have is mentioned in a House of Commons exchange as built in 1826 at the cost of £40,000!!, which is an astonishing amount to spend on a windmill! To compound this, none of the Victualling yard windmills are marked on maps.


I am baffled by a lovely watercolour of Deptford Theatre with pub adjoining dated 1840, showing a white smock mill apparently on the other side of the Creek in the corner. All the features of this  watercolour are well drawn and apparently accurate, but I have no windmill recorded in this spot. It looks like it is attached to a  factory, perhaps the soap factory(?), or the waterworks, so perhaps was  used for another function. 

A windmill called 'Clayton Mill', marked on Rocques map is still a mystery...

Monday 3 December 2012

Greenwich Peninsula - what do we know??

This really smashing picture has been passed to us by someone who would like to know more about it - and can we say that we have no idea who owns it, where it is or how it got to the person who sent it to us - so, sorry,  if it belongs to you - we will remove it if you want, or happy to share any information about the subject matter with you.
It apparently shows the Greenwich Peninsula's west bank by moonlight - we think soon after 1850.  Any ideas about any of the features shown on it. It seems to be taken from somewhere around Delta Wharf - and to show a boat builders yard, Cowden.  In the distance is Greenwich Hospital and - I am told Our Lady Star of the Sea.  Other buildings appear to be the telegraph cable works of what would have been at that date probably Glass Elliott.