The adulterations to which flour and bread are exposed usually consist in adding damaged or an inferior grade of flour to wheaten flour, or in disguising the presence of a poor quality of flour by the addition of mineral substances, such as: plaster, chalk, lime, alum, and sulphate of copper. Good flour has a white color, possessing a slightly yellow tinge, but is entirely free from red, grey or black specks. It is soft to the touch and adheres to the fingers, acquiring, when compressed in the hand, a soft cushion-like form. If mixed with water, it forms an elastic, homogeneous, but slightly coherent dough, which can be extended out in thin layers. Flour of an inferior quality possess a dull white color, and does not assume the cushion-like condition mentioned above, when pressed in the hand, but escapes between the fingers: the dough formed is of a poorer quality. Flour which has been damaged by moisture has a dull or reddish-white hue, and possesses a mouldy, or even a noxious, odor, as well as a bitter and nauseous taste which produces a marked acid sensation in the throat. Occasionally the presence of moisture causes the growth of _fungi_, the introduction of which in the digestive organs would cause serious results. The constituents of pure flour are: _Gluten._ _Starch_, in the proportion of 50 to 75 per cent. _Dextrine_, in the proportion of several per cent. _Glucose_, in the proportion of several per cent. _Salts_, remaining in the ash obtained by the calcination of the flour, in a proportion not exceeding 2 per cent. _Water_, of which it loses 12 to 15 per cent., at the heat of a water-bath, and 15 to 20 per cent., at a temperature of 160°. _Bran_, (ligneous and fatty matter,) in a very small proportion, when the flour has been properly bolted. In the process of bread-making, the gluten undergoes fermentation by the action of the leaven and liberates carbonic acid, which causes the dough to become porous and swell up, or, as it is termed, to _rise_. Bread contains the same substances as flour, but gluten and starch are present in a state that does not admit of their separation by mechanical means, and glucose, if present at all, exists in a smaller quantity: the proportion of dextrine and water is, on the other hand, considerably increased. The bread of the Paris city bakeries contains 40 per cent. of water--the crumb, which forms 5/6 of the weight of the bread, containing 45 per cent.; the crust, which constitutes the remaining 1/6, containing 15 per cent. In army bread 43 per cent. of water are contained--the crumb, which constitutes 4/5 of the weight of the bread, holding 50 per cent.; the crust which forms the remaining 1/5, containing 15 per cent. The addition of common salt naturally increases the proportion of ash left upon calcining bread.