among chemists, a method of stopping glass-vessels, used in chemical operations, so closely, that the most subtil spirit cannot escape through them.

It is commonly done by heating the neck of the vessel in a flame, till ready to melt, and then twisting it closely together with a pair of pincers. Or, vessels may be hermetically sealed, by stopping them with a glass plug, well luted; or, by covering the vessel with another ovum philosophicum.