346 BISMUTH 



mace, ginger, essence of lemon, neroli, or orange-flower water, called in technical 

 language, ' flavourings.' The kneading of these materials is always performed by 

 a kneading or mixing machine. The dough or pjste produced is passed severa'l 

 times between two revolving cylinders adjusted at a proper distance, so as to obtain 

 a flat, prfectly homogeneous mass, slab, or sheet. This is transferred to a stamping 

 or cutting machine, consisting of two cylinders, through which the sheet of homo- 

 geneous paste has to pass, and by which it is laminated to the proper thickness, 

 and at the same time pushed under a stamping and docking frame, which cuts it into 

 discs, or into oval or otherwise shaped pieces, as occasion may require. The stamps 

 or cutters in the frame being internally provided with prongs, push the cut pieces 

 of dough, or raw cakes, out of the cutting frame, and at the same time dock the 

 cakes, or cut pieces, with a series of holes, for the subsequent escape of the moisture, 

 which, but for these vents, would distort and spoil the cake or biscuit when put in 

 the oven. The temperature of the oven should be so regulated as to be perfectly 

 uniform, neither too high nor too low, but just at such a heat as is sufficient to give 

 the biscuits a light brown colour. For such a purpose the hot-water oven of Mr. 

 Perkins, or that of Mr. Roland, is the best that can possibly bo used. (See BREAD.) 

 Koland's oren offers the peculiar advantage that, by turning the screw, the solo of 

 the oven can bo brought nearer to the top, and a temperature is thus obtained suitable 

 for baking thoroughly, without burning, the thinnest cakes. 



_ One of the most curious branches of the baker's craft is the manufacture of 

 gingerbread, which contains such a proportion of molasses that it cannot be fer- 

 mented by means of yeast. Its ingredients arc flour, molasses or treacle, butter, 

 common potashes, and alum. After the butter is melted, and the potashes and alum 

 are dissolved in a little hot water, these throe ingredients, along with the treacle, are 

 poured among the flour which is to form the body of the bread. The whole is then 

 incorporated by mixture and kneading into a stiff dough. Of these five constituents 

 the alum is the least essential, although it makes the bread lighter and crisper, and 

 renders the process more rapid ; for gingerbread, dough requires to stand over for 

 several days, some 8 or 10, before it acquires the state of porosity which qualifies it 

 for the oven ; the action of the treacle and alum on the potashes, in evolving carbonic 

 acid, seems to be the gasifying principle of gingerbread ; for if carbonate of potash 

 is withheld from the mixture, the bread, when baked, resembles in hardness a piece 

 of wood. 



Treacle is always acidulous. Carbonate of magnesia and soda may be used as 

 substitutes for the potashes. Dr. Colquhoun has found that carbonate of magnesia 

 and tartaric acid may replace the potashes and the alum with great advantage, 

 affording a gingerbread fully as agreeable to the taste, and much more wholesome 

 than the common kind, which contains a notable quantity of potash. His pro- 

 portions are 1 Ib. of flour, of an ounce of carbonate of magnesia, and & of an ounce 

 of tertaric acid, in addition to the treacle, butter, and aromatics, as at present 

 used. The acid .and alkaline earth must bo well diffused through the whole 

 dough ; the magnesia should, in fact, bo first of all mixed with the flour. The molted 

 butter, the treacle, and the acid dissolved in a little water, are poured all at once 

 amongst the flour, and kneaded into a consistent dough, which being set aside for half 

 an hour or an hour, will bo ready for the oven, Jind should never bo kept unbaked for 

 more than 2 or 3 hours. The following more complete recipe is given by Dr. Colqu- 

 houn for making thin gingerbread cakes : Flour 1 Ib., treacle Ib., raw sugar Ib., 

 butter 2 ounces, carbonate of magnesia ounce, tertaric acid ounce, ginger ^ ounce, 

 cinnamon ounce, nutmeg 1 ounce. This compound has rather more butter than 

 common thin gingerbread. In addition to these, yellow ochre is frequently added by 

 cheap gingerbread makers, and altogether this preparation, more generally consumed 

 by children, is very objectionable. 



Within the last few years there has been a very remarkable development of the 

 trade in biscuits. Biscuits of all sorts, and really many curious and agreeable 

 varieties, are now manufactured on a large scale, and machinery has been created to 

 facilitate the process. 



BISMUTH. (Bismuth, Fr. ; Wismuth, Ger.) Symbol, Bi. ; Atomic weight, 210. 

 The metal bismuth occurs chiefly in a native state, but is also found in certain combi- 

 nations, forming the ores noticed in the following list of bismuth-bearing minerals : 

 Native Bismuth is whitish, with a faint reddish tinge, and a metallic lustre which 

 is liable to tarnish. Streak, silver-white. Hardness, 2 to 2'5 ; specific graA'ity, 9'727- 

 It is brittle when cold, but slightly malleable when heated. It generally occurs crys- 

 tallised or in a dendritic form. It fuses readily at 476 F. Beautiful crystals can bo 

 formed artificially by fusion and subsequent slow cooling. The native metal frequently 

 contains silver, arsenic, or tellurium. It is the source of all the metal used in tho 

 arts, 



