question Military Compass

[LarryH57]

I bought my son a compass off the web and it has a bubble in it. The seller says it is normal as it is designed to show the user when he is holding it level, however it already has a separate spirit level next to the dial for this very purpose.

 

Is the wool being pulled over my eyes? I can't say I remember such a bubble being in the compass when I was doing map reading in the Army?

 

Also its strange that none of the photos of the item show the bubble, neither does the photo on the box.

Edited January 16, 2015 by LarryH57

[MB1944]

It would be helpful to see a picture of the compass to identify it.

[Tony B]

There will always be some air in the compass, assuming it is liquid damped. Does the liquid cover the card? If so it will damp the card, which is what it should do.

[Richard Farrant]

The fluid in there is to damp the movement of the needle. Small bubbles in the liquid-filled capsule have no influence on compass accuracy. They may appear or disappear in response to changes in temperature and atmospheric pressure. May want to put it somewhere warm. If a bubble larger than 1/4 inch diameter appears, the capsule may be damaged or leaking and will need to be replaced.

[LarryH57]

Many thanks for your replies; the bubble is about 1/4th inch already but if it has no bearing on the accuracy then that's OK by me.

[Tony B]

You can get replacement fluid. It is sometimes nessacary in marine compasses. http://www.trademarklondon.com/Compass-Fluid/