Further to this subject, I alerted Peter Ransom to the thread and he has asked me to send on the following references that may prove useful:
Kiely, ER 'Surveying instruments, their history and classroom use' (NCTM yearbook) New York 1947. I had not seen a copy of this on the market for 10 years, until today! It is in Graham Weiner's book list at £25 (phone 01818838424) I do have my own copy, and it is brilliant. Cross staff, quadrant, etc - everything you want to make your own. Taylor EGR & Richey MW 'The Geometrical Seaman' Institute of navigation 1962 This is also very informative, with a short chapter of each instrument including the cross staff. I have a copy which I do read from time to time, as it's also a good story. Daumas M 'Scientific instruments of the 17th & 18th centuries and their makers' 1972. Very interesting book with two pages describing the cross staff. Ransom PH 'The ACD of old instruments' Mathematics in School Oct 93 My favourite work on the subject. Describes how to construct and use a cross staff with school children. Highly illustrated. Can supply a photocopy if anyone wants. £1 to cover my costs in the UK. To you, my boy, it's free - just ask! It is older than suggested. Reputedly it was invented by Levi ben Gerson (1288 - 1324 (or 1344 depends on reference)), but by 1581 it had achieved the form which it retained until it became obsolete. Hope this is of interest. Patrick (well, Peter really!)
