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It is objected by opponents of the Dauglish system that the product is not really bread, but only an artificial pro duct resembling bread. It is held that the process of fer mentation has a specific influence ou the constitution of bread, beyond its mechanical effect of rendering the mass spongy or porous. One of the chief hindrances to the more general use of aerated bread is the fact that it is, as com pared with fermented bread, insipid and tasteless. In practice, the public have not hitherto derived any advan tage from the alleged economy of manufacture, and the suitability of inferior and cheap flour for the process. Al though fermented bread is hurtful in some conditions, it is not easy to supplant well-made fermented loaves in general public estimation, and aerated bread can scarcely be said to have hitherto had a fair trial, as with the necessarily expensive machinery a large trade is necessary in order to return a fair profit on the capital invested.

Unfermented Bread.—Under this head is included such bread as is vesiculated by means of carbonic acid evolved from chemical substances introduced in the making of the dough. In writing the article on &quot; Baking &quot; for the supple- meat to the fifth edition of this Encyclopaedia, published in 1816, Professor Thomas Thomson of Glasgow stated that the only end served by fermentation was the genera tion of carbonic acid gas, aud that this might bo accom plished by the use of hydrochloric acid and bicarbonate of soda. About 1842 Mr Henry Dodson commenced to manufacture bread on this system, and obtained a patent for his process. He used hydrochloric acid and bicarbon ate of soda in such proportions that while, by their re action, they liberated sufficient carbonic acid to aerate the dough, they formed chloride of sodium or common salt enough for the bread. Liebig, in his Familiar Letters, says regarding this system : &quot; Chemists, generally speak ing, should never recommend the use of chemicals for culinary preparations, for chemicals are seldom met with in commerce in a state of purity. Thus, for example, the muriatic [hydrochloric] acid which it has been proposed to mix with carbonate of soda in bread is always very impure, and very often contains arsenic.&quot; The sesquicarbonate of ammonia is also used as a source of carbonic acid in vesiculating bread, and it, on account of its highly volatile nature, is entirely driven off ia the process of baking. A great amount of private or domestic baking is conducted on the same principle, butter milk and bicarbonate of soda being used for mixing the dough in making &quot; scones.&quot; In this case the lactic acid of the milk combines with the soda, liberating carbonic acid. The baking powders and yeast powders which are sold, and the so-called self-raising flour, all depend for their action on the mixture of bicar bonate of soda with some organic acid, such as tartaric or citric acid.

Baking Machinery and Ovens.—The art of baking, al though it is the most important of all industries connected Machinery with the preparation of human food, is one which is still carried on in the most rude and primitive manner. While modern inventions and the progress of improvement have changed the conditions under which nearly all arts and manufactures are conducted, the baking of bread is still conducted as it was during the palmy days of ancient Greece. The nature of the processes necessary for the preparation of bread, the limited time it will keep, and the consequent impossibility of storing the product or send ing it any considerable distance, tend to keep the trade in the position of a limited and local handicraft. It is, there fore, not a pursuit which attracts capitalists, and master bakers are mostly in the position of small tradesmen, with out either the inclination or ability to invest money in expensive machinery and fittings. In the case of biscuit- baking the conditions are quite different, and it, as has been seen, has developed into a great manufacture, with elaborate and complex machinery and the most perfect mechanical appliances. Many forms of machine have been proposed as substitutes for the rude and laborious manual labour always unfavourable to health, and sometimes not very cleanly involved in baking. Many of these machines admittedly produce better bread than can be made by hand work, and that at no inconsiderable saving of material and time, but the necessity of either steam or water power for their effective working greatly restricts their use. 4. Kneading Macnii.e. The two processes to which machinery has been success fully adapted, are the mixing of the sponge and the knead ing of the dough. Attempts have been made to mould loaves by machinery, but these have hitherto failed ; nor has the endeavour to fire bread in travelling ovens yet been practically successful. A great variety of knead ing machines have been suggested and used, since the first trial of such an implement in Paris upwards of a century ago. The various plans upon which such machines have been constructed will be seen in the accompanying illustrations. Fig. 4 is a form of dough-making machine in common use. It consists of a trough or box, the lower portion of which is semi-cylindrical, hung on a spindle, with a series of iron crossbars revolving inside. It is made to be worked by either hand or steam-power, and of various sizes, as required by bakers. In this machine the whole of the operations connected with setting the sponge, breaking the sponge, and mixing the dough, are performed. The gearing is arranged to give a fast motion for setting the sponge, and a slow motion towards the close of the dough making, when it is desirable to draw out the n:nss in order to give it a &quot;skin,&quot; or smooth superficial texture. A worm-wheel, working in toothed gearing, tilts over the machine when the process of kneading is complete, and the dough is then conveyed to the scaling and moulding table. 