A few slips of paper applied round the neck of the vessels with common size will be sufficient to keep in such vapours as are aqueous or not very spirituous. If the vapours are more acrid, or more spirituous, recourse may be had to slips of bladder long steeped in water, which containing a sort of natural glue, close the junctures of the vessels very well. If it be required to confine vapours of a still more penetrating nature, it will be proper to employ a lute that quickly grows very hard; particularly a paste made with quick-lime and any sort of jelly, whether vegetable or animal; such as the white of an egg, stiff size, _&c._ This is an excellent lute, and not easily penetrated. It is also used to stop any cracks or fractures that happen to glass vessels. But it is not capable of resisting the vapours of mineral acid spirits, especially when they are strong and smoking: for that purpose it is necessary to incorporate the other ingredients thoroughly with fat earth softened with water; and even then it frequently happens that this lute is penetrated by acid vapours, especially those of the spirit of salt, which of all others are confined with the greatest difficulty. In such cases its place may be supplied with another, which is called Fat Lute, because it is actually worked up with fat liquors. This lute is composed of a very fine cretaceous earth, called tobacco-pipe clay, moistened with equal parts of the drying oil of lint-seed, and a varnish made of amber and gum copal. It must have the consistence of a stiff paste. When the joints of the vessels are closed up with this lute, they may, for greater security, be covered over with slips of linen smeared with the lute made of quick-lime and the white of an egg. Chymical vessels are liable to be broken in an operation by other causes besides the sudden application of heat or cold. It frequently happens, that the vapours of the matters exposed to the action of fire rush out with such impetuosity, and are so elastic, that, finding no passage through the lute with which the joints of the vessels are closed, they burst the vessels themselves, sometimes with explosion and danger to the operator.