Let the Receivers be made of glass, or of strong earth, which may retain the spirits, and such is the Waldburgick, Hassiack, Frechheimensian, Siburgic earth, _&c._ They are better that are made of glass, if they are to be had, and those especially which are made of strong and firm glass, which may be smoothed about the joints with a Smiris stone, and so fitted that they may the better be joyned together, and then they need not luteing (but how they shall be smoothed with the Smiris stone, and be fitted, shall be taught in the Fifth part, which treats of Manuals) because by this means they are joyned so close, that no spirits can go through the joynts: otherwise you must close the joynts with the best Lute, such as will not let the spirits exhale, which shall be taught in the Book treating of Manuals. The form of the recipient you may see in the delineation thereof. As for the quantity thereof, know that by how much the greater they are, so much the better they are, for then you need the fewer, but the more, by how much the lesser they are. Let the superiour orifice be larger than the inferiour, so that alwaies another receiver may with its inferiour orifice be joyned to it, and let the inferiour orifice have a Diameter of three fingers breadth, or thereabouts; I mean in case the Diameter of the Furnace be of one span. For a greater Furnace requires greater holes, as also orifices of the receivers, by which means a sufficient and due proportion of air may be given to the fire: or if the Diameter of the Furnace be more than a span, it must also have two or three pipes (which being considered together, should have a wideness answering the wideness of the third part of the Furnace, for so great a wideness, and so much air is required, if the fire burn freely and do its office) to which vessels of the aforesaid proportion must be applyed, that the fire be not choaked.