heat generally effects considerable changes in the different principles of which they are composed. Thus, bread from wheat is no longer capable of forming a paste with water, such as can be made with flour; nor can starch, and gluten, elements existing in flour, be obtained from it after it has been baked in bread. The alteration in potatoes by the culinary process is even more considerable.

The farinaceous vegetables used for making bread, are chiefly wheat, barley, oats, rye, buck wheat, maize, beans, pease, rice, potatoes, &c. In times of scarcity, other substances have been used, as acorns, chesnuts, &c.

Of all these wheat is found to afford the best bread, and we shall begin by describing it. Wheat flour, when analysed, is found to consist of — 1. Gluten. 2. Fecula, or starch. 3. Saccharine matter, or mucilage.

The gluten is very elastic, of a greyish white colour, and when drawn out to its fullest extent, has the appearance of animal membrane. In this state, it adheres to many bodies, and forms a very tenacious glue, which has been used for mending broken porcelain. It is insoluble in water, alkohol, ether, or oil; and, in many of its properties, it resembles animal substances.

The fecula is a delicate white powder, soft to the touch, scarcely sensible to the taste, almost insoluble in cold water, but soluble in warm water.

The saccharine part is a sugar similar to what is contained in other vegetables.

These three constituent principles are easily separated from each other in the following manner. Knead some flour with water, and let a stream of water constantly flow over it. The fecula, or starch, will be carried off by the water, and will

fall to the bottom of the vessel where it is collected; the sugar will be held in solution in the water em- . ployed, and the gluten will remain alone.

There are three sorts of bread in general use, prepared from wheat flour: 1. Unleavened bread. 2. Leavened bread. 3. Bread made with yeast.

Unleavened Bread.

When flour is kneaded with water, it forms a tough adhesive paste, containing the constituent principles of flour, with little or no alteration, and not easily digested by the stomach.

When formed into cakes, and baked by heat, the gluten, and probably the starch, undergo a considerable change, and the compound is rendered more easy of digestion.

Bread made in this manner, without any addition, is called unleavened bread. It is not porous, but solid and heavy.

This is, no doubt, the most ancient method of preparing bread, and it is still used in many countries. The oat cakes, and barley bread, used in Scotland, and the north of England, are of this kind; so are also biscuits of all kinds.

Unleavened bread is also used by the Jews during the Passover.

Of Leavened Bread.

When flour is kneaded with water, it is called dough; and when this is kept in a warm place, it swells up, becomes spongy, and is filled with air. bubbles; it disengages at length an acidulous and spiritous smell, tastes sour, and in this state is called leaven.

Here the saccharine part has been converted into ardent spirit, the mucilage tends to acidity,

and the gluten probably verges towards a state of putridity. By this incessant fermentation, the mass is rendered more digestible and light, that is, it becomes much more porous by the disengagement of elastic fluid, which separates its parts from each other, and much enlarges its bulk. The operation of baking puts a stop to this process, by evaporating a great part of the moisture, which favours the chemical attractions, and probably also by further changing the nature of the component parts. Bread, however, in this state, will not possess the requisite uniformity. In order to promote an uniform fermentation, a small portion of leaven is intimately blended with a quantity of other dough, which, by the aid of heat, diffuses itself, and causes all the parts to ferment at the same time, As soon as the dough has acquired a sufficient bulk from the extrication of carbonic acid gas, it is considered as fit for the oven. It will be necessary here to consider more at large the nature of the fermentation, which is so essential in the making of good bread.

When wheat-flour and water are mixed, the saccharine extract of the flour, in consequence of heat and moisture, has its constituent principles disunited; the oxygen seizes the carbon, forming carbonic acid, which flies off in the form of gas, and occasions that internal motion and increase

which appears. This process, if left to itself, is extremely slow, and is therefore accelerated by the addition of more dough and warm water, The gluten, being dispersed through every part of the mass, forms a membrane among the dough, which suffers the carbonic acid gas to expand, but prevents its total escape, thus causing that porous reticulated appearance, which fermented bread

always has. As soon as the dough begins to sink, it is made up into the proper form, and put into the oven, where the heat converting the water into an elastic vapour, the loaf rises still more. The fermentation by means of leaven is thought to be of the acetous kind, because it is generally so managed that the bread has a sour taste.

Bread made with Yeast.

Yeast is the froth formed upon the surface of beer, or ale, in a state of fermentation, and is composed of carbonic acid gas inclosed in bubbles of the mucilaginous liquor. When this is mixed with dough, it causes it to ferment, and rise better and more quickly than ordinary leaven; and by this means the best bread, and that now most generally in use, is made.

Bread made with yeast is not only less compact, lighter, and of a much more agreeable taste than the preceding kinds; but it is also more miscible in water, with which it does not form a viscous mass, a circumstance of the greatest importance in digestion.

Bread, if well baked, is materially different from flour and farinaceous cakes; it no longer forms a tenacious dough with water, nor can starch or gluten be any more separated from it: and hence most probably its good qualities result.

The method of making common family bread is as follows: to half a bushel of flour add six ounces of salt, a pint of yeast, and six quarts of water that has boiled; in warm weather pour the water in nearly cold, but it winter let it be lukewarm. Put all these into a kneading-trough, and work them together till they are the proper consistence of dough. Cover up the dough warm that it may

ferment and rise. This is called setting the sponge. After letting it lie the proper time, an hour and a half, more or less, knead it well together, and let it lie some time longer covered up. The oven must in the mean time be heated: when this is done, and it is properly cleaned, make the bread into loaves, and place them in the oven to bake.

Household bread, or brown bread, is baked in the same manner, only of flour that is made from the whole of the wheat, the bran as well as the flour being ground together; whereas in the white bread, the coarser part of the bran is separated from the flour. In what is called French bread, the fermentation is carried on longer than in common bread, by which it becomes more porous, and consequently lighter. Some bakers make a superior kind of French bread, by putting together a peck and a half of the finest wheaten flour, called Hertfordshire white, a pint of milk, a quarter of a pound of salt, a pint and half of yeast, a quarter of a pound of butter, two eggs, and three quarts of water; it is baked nearly in the same manner, only frequently turning the bread in the oven.

The process used by the bakers for making bread varies from what has been described, only in circumstances depending on the great quantity that is baked at a time. It is said that they are apt to adulterate the bread sometimes with alum, and also with chalk, and for this they are severely punishable; and any one suspecting it may easily detect it by cutting a loaf in slices, and mixing it with water which will dissolve the alum: and it may then be obtained by evaporation.

Bread is made from the farinaceous grains; but of these, barley, oats, and rye, are most generally used in Great Britain next to wheat. Wheat alone