NavList:

Tony, both bubble units are made of metal. The black one has a "vapour pressure" bubble chamber in which a diaphragm is pulled out to lower the pressure in the bubble chamber until a bubble pops out of the volatile fluid inside (xylene). The shiny, large one has an air bubble chamber, in which fluid is sucked out, admitting a bubble of air from an air chamber, or the air sucked out, admitting flui to make the bubble smaller. Nearly always the fluid has leaked out over the years.

Each bubble unit has its problems for restoration to working order, made much easier by the advent of thin Viton O rings. If you look at my web site www.sextantbook.com and search under "bubble chambers" you will get an idea of what awaits you.

Bill Morris

Pukenui

New Zealand