NavList:

David,  A book that talks about early navigation in baloons and Zepplins is " Most Probable Position" by Monte Wright.  In it he describes sextants with bubble levels - marine sextants with an artifical horizon - that were tried in baloons in the late 1800's and German Zepplins during WW1.
I have bought several so-called baloon sextants on e-bay.  They are misslabled by the seller.  The correct term is Pibal - pilot baloon transit.  The instrement looks like a theodolite or transit but the eyepiece is at 90 degrees to the objective lens.  The eyepiece is in the horsontian axis.  You can keep the baloon in sight even if it flys overhead.
There is a Navy model for use on ships that looks something like a big - heavy sextant but is monten in gimbles.
Hope this helps.  John H.

Thank you John.  As I suspected, the later models are mislabelled, and are actually for tracking balloons (or anything else that flies over I suppose).  It's their use from balloons and airships I'm researching.  I've just found a copy of MPP on Abe Books UK from the same US bookseller at a price I can afford, so I'll wait until that arrives.  (I've plenty of info after 1918 by the way) DaveP