Tapering Mercury Barometer

Jul 2015
I am curious if the height of the Mercury column inside a Toricellian Mercury Barometer be the same if we use a tapering / stepped (unequal inner diameter) glass tube as depicted in the image below instead of a regular constant ID one?

Note: I know that the ID of a barometer tube does not affect the Mercury column height as long as the ID of the tube remains the same.

Last edited:
Apr 2015
Somerset, England
The height of the mercury column does not depend on the shape of the tube, only the air pressure.

So yes the tube could be tapered, stepped, triangular, step out then step in again or anything you like really.

The only constraint is that the tube is wide enough so that it is not a capillary.
Then the mercury might act like the liquid in a medical thermometer.