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Dear all Thanks for your help on this one. Apparently this is called 'hydrostatic levelling' and is a well established technique that has been used in nuclear power plants, to level Dutch canals and to measure the tidal tilting of floating ice. Thanks again Anne At 11:08 13/05/2004, Anne Taylor wrote: >Dear All >I'm in correspondence with someone who is writing about his time as a >surveyor during and after WWII. He has asked if Frank Debenham ever wrote >about the surveying/levelling technique outlined in the message below. I've >looked in Debenham's books 'Excercises in cartography' and 'Map Making' and >a colleague in the Department of Geography at Cambridge has looked through >their collection of Debenham articles - but without success. >Does anyone know of a reference to this technique - by Debenham, or anyone >else? >Many thanks >Anne > > >>Dear Anne, >> >>Here I am still pegging away and peering into my dim and (literally) >>distant past! >> >>One small incident I have just remembered was the visit to the Survey >>Department in Khartoum by a Prof. Frank Debenham a well known Cambridge >>geographer. >> >>He was demonstrating a levelling device which consisted of a long plastic >>tube connected at both ends to a graduated glass tube about six feet long >>attached to a wooden staves. >> >>In operation you filled the device with a suitable quntity of water and >>then by holding the staves vertically you had a levelling device which >>could be used through (say) thick bush where normal levelling using a >>spirit level was unsuitable. >> >>I never heard of this device again but I suspect that it was probably >>written up at the time. Any chance of finding a reference to it? >> >>With best wishes, >> >>Bill Saunders > >Anne Taylor >Head of Map Department, Cambridge University Library, West Road, Cambridge >CB3 9DR >Tel: 01223-333041. Fax: 01223-333160. email: [log in to unmask] >http://www.lib.cam.ac.uk/maps/Home.htm Anne Taylor Head of Map Department, Cambridge University Library, West Road, Cambridge CB3 9DR Tel: 01223-333041. Fax: 01223-333160. email: [log in to unmask] http://www.lib.cam.ac.uk/maps/Home.htm