inner coat of a calf's stomach: the effect being due, in the latter case, to the gastric juice of the stomach. This is the course taken in making cheese. In order to make the best cheese, milk, which has stood a sufficient time, but has not been deprived of its cream, is heated very gradually, till it reaches the temperature at which it curdles; the rennet is then added; the curd is cut into small slices, and the whey gently removed, by suspending the whole mass in a bag. In this way, the cream is retained, and the flavor and richness of the cheese much improved. If the coagulation takes place suddenly, owing to too much heat, and the whey is speedily removed, most of the cream is carried off, and the cheese is poor, and without flavor. To make poor cheese is easy; but to make good cheese is altogether the most difficult operation which devolves on the housewife. It requires a proper regulation of the temperature of a dairy, since too much heat causes the milk to sour, and too little interferes with the process of curdling. It requires, also, the selection of proper utensils, and the most scrupulous care in cleansing them. The acid contained in milk (and which is now known to be acetic acid) will act upon copper, brass, or lead, and even upon earthen vessels, if they have been glazed with lead, producing a poisonous compound. Hence, vessels made of these materials should never be used for holding milk. Even tin is not unobjectionable, since it is apt to combine, in a slight degree, with this acid, and thus a compound is formed, which adheres so closely to the vessel, that it can be removed only by the most careful washing, and which emits a disagreeable, fetid odor. In addition to this, the greatest care must be used, in heating and curdling the milk, so that it do not take place too suddenly; that the cream be retained, and yet that the whey be entirely expressed. The constant and unremitting attention requisite, in making cheese, is thus described by Sir John Sinclair, the eminent agriculturist. "If," says he, "a few spoonfuls of milk are left in the udder of the cow, at milking; if any

one of the implements used in the dairy be allowed to be tainted, by neglect; if the dairyhouse be kept dirty, or out of order; if the milk is either too hot or too cold at coagulating; if too much or too little rennet is put into the milk; if the whey is not speedily taken off ;the milk will be in a great measure spoiled. If these nice operations," continues he, "occurred only once a month, or once a week, they might be easily guarded against; but as they require to be observed during every stage of the process, and almost every hour of the day, the most vigilant attention must be kept up, through the whole season." Another author remarks, that "cheese varies in quality, according as it has been made of milk of one meal, of two meals, or of skimmed milk and that the season of the year, the method of milking, the preparation of the rennet, the mode of coagulation, the management of the cheese in the press, the method of salting, and the management of the cheese-room, are all objects of the highest importance to the cheese-manufacturer; and yet, notwithstanding this, the practice, in most respects, is still regulated by little else than mere chance, or custom, without the aid of enlightened observation, or of well-conducted experiment."

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The cream, which rises to the top of milk, consists of butter; caseous matter, which is the basis of cheese; and whey. If cream be put into a sack, and suspended, so that the whey may run off, the remainder will be cream cheese. If it be put into a vessel, and agitated, the butter assumes a solid form, and may be entirely separated from the whey and caseous matter by washing and kneading it. Whether the butter naturally exists in the cream or milk, and is distributed through it by means of mechanical suspension; or whether it is formed from it, during the process of churning, by certain chemical changes, which then occur, is not well known. The latter seems the most probable opinion. churning is attended by important chemical changes is certain. In all cases, considerable gas is extricated which is supposed to be carbonic acid gas. Oxygen

That

also seems to be absorbed, and to this is probably owing the consistence of butter; since the oils are found to thicken, by exposure to oxygen. If these two changes do take place, they may serve to explain the fact, which is well known to butter-makers, namely, that butter is made much better and quicker, from cream slightly acid, than from that which is sweet; and that still the butter will be sweet, and the whey or buttermilk much less sour than the cream had been. The carbonic acid, which produces the acidity, escapes during the churning.

To make good butter requires constant care and cleanliness. The milk should be kept not only in a clean and well-aired apartment, but in one, also, in which the temperature is regulated. Too much heat sours the milk before the cream forms; and too little prevents it from forming in proper quantities, and imparts to it a bitter and disagreable taste. Churning, too, is a delicate process. It must always take place in about the same temperature, and hence the practice, which seems at first view inconsistent, of cooling the cream in Summer, during the churning, and warming it in Winter. The agitation, too, of the cream, should be kept up, without interruption, otherwise the butter will go back, as it is called, and it must not be too quick and violent, for fear of imparting a disagreeable flavor to the butter. We need say nothing of the care requisite in working off the whey and caseous matter, applying salt, packing down, &c. It may not be amiss to remark, that "it is ascertained, by observation, that the milk, given by an animal during the latter half of the milking process, yields much more cream, than that which is obtained at first; and also that the cream, which first rises after the milk has been deposited in the dairy-pans, is both much greater, in a given space of time, than that which rises in an equal space several hours after, and of a greatly superior quality; that thick milk throws up less cream than thin, but of a richer quality; and that milk, that has been much agitated by carrying, and cooled

before it is put into the milkpans, never throws up so much cream as that which is immediately deposited in them after milking. It is also known, that the milk is not the best, till about four months after the cow has calved; and that the degree of heat, most favorable to the production of cream from milk, is from fifty to fiftyfive degrees Fahrenheit."

4. The preserving of Food.-All vegetable and animal substances are liable to decay. This is owing to certain affinities which the different principles, composing these substances, have for each other and for surrounding bodies, stronger than those which had previously united them, and which inclines them, as soon as the living principle is extinct, to decompose and form new compounds. Thus, the carbon and hydrogen, which are found in all organized bodies, tend to appropriate to themselves so much oxygen, as shall convert them into carbonic acid and water. In the case of animal bodies, this tendency to decomposition is stronger than in vegetables, since, in addition to the three principles just named, which they have in common with all vegetables, they contain nitrogen, or azote, an element not found in most plants, and which has a strong affinity for all the above principles, especially for hydrogen.

This disposition to decay, though it exists from the moment that the vital principle is extinct, will not so soon manifest itself, without the aid of moisture, air, and a certain temperature. It is well known, in the first place, that substances kept in moist situations putrefy much sooner than in those which are dry. The water probably acts, by softening the texture; and thus counteracting the agency of cohesion, which tends to keep the substance in its original state: a part of the effect may be owing, also, to the affinity of the water for some of the products of the putrefaction. Hence the importance of excluding all substances, which we would preserve, from moisture. Meat, thoroughly dried, may be kept a very long time. So may fruit, if carefully freed from all moisture, and kept in a dry apartment, or

packed in some substance which will absorb the moisture that may chance to collect, or exposed to a uniform heat, sufficient to expel the watery particles.

Air contributes to putrefaction, by uniting its oxygen with the carbon and hydrogen of the decaying substance. Hence, if we would preserve food, for a great length of time, we must endeavor to exclude the air, also. This is done, in the case of fruit, by putting it in bottles, from which the air had been previously expelled, by heat, and then sealing them up, air-tight. Another method has been brought into notice recently, called, Appert's process. The articles to be preserved are enclosed in bottles, which are filled to the top with any liquid; for example, with the water in which the article, if solid, has been boiled. The bottles are closely corked and cemented, to render them hermetically tight. They are then placed in kettles filled with cold water, and subjected to heat, till the water boils. After the boiling temperature has been kept up, for a considerable time,-in some cases an hour, but varying with the character of the articles to be preserved,-the bottles are suffered gradually to cool. In this state, meats, vegetables, fruits, milk, and other substances, are preserved, perfectly fresh, without any condiments, for long periods of time; in some instances, for the space of six years. Instead of bottles, tin canisters are sometimes used, and rendered tight by soldering. The remarkable effect of this process is to be attributed, not altogether, perhaps, to the exclusion of atmospheric air, since some will remain in the liquid and other substances; but in part, also, to the influence which the heat has had, in fixing the small portion of atmospheric oxygen, that is present, by combining it with some principle in the other substances, so that it is no longer capable of exciting the fermentative action, which, in parallel cases, leads to decomposition.

The influence of certain temperatures, in promoting decay, is well known. In warm seasons and in hot climates, every thing tends to corruption. The heat acts,