|MadSci Network: Other|
This question is outside of my area of expertise. However, there are only several fluids used in compasses, gages, etc. that I know of. Of more importance is the viscosity of the mixture, usually mixed with a solvent (water or alcohol) Fluids commonly used are: Water - probably not in this case, could freeze Alcohol - possibly Glycerol - possibly, if thinned out Ethylene Glycol - green tint, possible if thinned out. A couple of web sites I found; although not containing the answer are: http://ourworld.compuserve.com/homepages/silvauk/homepage.htm http://www.silva.se/files/history1.html
Try the links in the MadSci Library for more information on Other.