The first layer is the same earth with the rest, sifted very fine ; whilst it is tem pering in water, it is mixed with cow's hair, to make it cohere. The whole, be. ing a thin cullis, is gently poured on the model, that fills exactly all the sinnosities of the figures, &c. and this is repeated till the whole is two lines thick over the mo del. When this layer is thoroughly dried, they cover it with a second of the same matter, but something thicker : when this second layer becomes of some consist ence, they apply the compasses again, and light a fire in the core, so as to melt off the wax of the inscriptions, &c.
After this, they go on with other layers of the shell, by means of the compasses. Here they add to the cow's hair a quanti ty of hemp, spread upon the layers, and afterwards smoothed by the board of the compasses. The thickness of the shell comes to four or five inches lower than the mill-stone before observed, and sur rounds it quite close, which prevents the extravasation of the metal. The wax should be taken out before the melting of the metal.
The ear of the bell requires a separate work, which is done during the drying of the several incrustations of the cement. It has seven rings ; the seventh is called the bridge, and unites the others, being a perpendicular support to strengthen the curves. It has an aperture at the top, to admit a large iron peg, bent at the bot tom ; and this is introduced into two holes in the beam, fastened with two strong iron keys There are models made of the rings, with masses of beaten earth, that are dried in the fire, in order to have the hollow of them. These rings are gently pressed upon a layer of earth and cow's hair, one half of its depth ; and then taken out, without breaking the mould This operation is repeated twelve times for twelve half-moulds, that two and two united may make the hollows of the six rings : the same they do for the hol low of the bridge, and hake them all, to unite them together.
Upon the open place left for the coals to be put in are placed the rings that con stitute the ear. They first put into this open place the iron ring to support the clapper of the bell ; then they make a round cake of clay, to fill up the diameter of the thickness of the core. This cake, after baking, is clapped upon the open ing, and soldered with a thin mortar spread over it, which binds the cover close to the core.
The hollow of the model is filled with an earth sufficiently moist to fix on the place, which is strewed at several times upon the cover of the core ; and they beat it gently with a pestle to a proper height ; and a workman smooths the earth at top with a wooden trowel dipped in water.
Upon this cover, to be taken off after wards, they assemble the hollows of the rings. When every thing is in its pro per place, they strengthen the outsides of the hollows with mortar, in order to bind them with the bridge, and keep them steady at the bottom, by means of a cake of the same mortar, which fills up the whole aperture of the shell. This they let dry, that it may be removed with out breaking. To make room for the me tal, they pull off the hollows of the rings through which the metal is to pass, be fore it enters into the vacuity of the mould. The shell being unloaded of its ear, they range under the mill-stone five or six pieces of wood, about two feet long, and thick enough to reach almost the lower part of the shell; between these and the mould they drive in wooden wedges with a mallet, to shake the shell of the model whereon it rests, so as to be pulled up, and got out of the pit.
When this and the wax are removed, they break the model and the layer of earth, through which the metal must run, from the hollow of the rings, between the bell and the core. They smoke the in side of the shell, by burning straw under it, that helps to smooth the surface of the bell. Then they put the shell in the place, so as to leave the same interval between that and the core ; and before the hollows of the rings or the cap are put on again, they add two vents, that are united to the rings, and to each other, by a mass of baked cement. After which they put on this mass of the cap, the rings, and the vent, over the shell, and solder it with thin'cement, which is dried gradually, by covering it with burning coals, Then they fill up the pit with earth, beating it strongly all the time round the mould.
The furnace has a place for the fire, and another for the metal. The fire place has a large chimney, with a spa cious ash-hole. The furnace, which contains the metal, is vaulted, whose bot tom is made of earth, rammed down ; the rest is built with brick. It has four apertures ; the first, through which the flame reverberates ; the second is closed with a stopple, that is opened for the me tal to run ; the others are to separate the dress, or scoria, of the metal by wooden rakes : through these last apertures pass es the thick smoke. The ground of the furnace is built sloping, for the metal to run down.