On 2 Mar, 12:51, Bruce wrote:

There is a standard method of adjusting a Dumpy level that should be
found in every basic guide to surveying.

Or more usefully, it's probably in "Brickwork" vol 3 too, which is
worth having and is also on Google books
http://books.google.co.uk/books?id=i...fox-a#PPA83,M1

I was trying to set up a SiteSquare the other day and was pleasantly
surprised to find that the web's best effort then turned out to be
this book, which was already on the shelf within arm's reach - I'd
forgotten it did optics too.