manner of stopping or capping glass vessels, for chemical operations, so very accurately, that nothing can exhale or escape, not even the most subtle spirits. It is performed by heating the neck of the vessel in the flame of a lamp till it be ready to melt, and then with a pair of pincers twisting it close together. This they call putting on Hermes's seal. There are also other ways of sealing vessels hermetically; viz. by stopping them with a plug or stopple of glass, well fitted into the neck of the vessel; or, by turning another ovum philosophicum upon that wherein the matter is contained.