them to the cause of science. One of these, after analyzing, was put into an air-tight inclosure, and the air within it tested from time to time. The enclosed air began to change right away, and in a few days the oxygen was all gone, and in its place were found carbonic acid gas and the vapor of water. After determining the water and gas, the vessel was exhausted and refilled with air, the oxygen disappearing and the gas and water reappearing, as they did before. These tests were repeated till the cheese became cured, the loss of oxygen and development of gas and water decreasing gradually as the ripening of the cheese went on. A second cheese was treated in the same way, with similar results, and a third, after it had begun to cure, was put into confined air and left some three or four months (the exact dates not being kept), and at the end of the time was found to have made no perceptible change. Analyses were made from time to time, and the loss of substance noted. The estimation of the water which escaped, and the amount left in the cheeses when cured, showed that a considerable increase of water had been going on while the cheese were curing. The results here determined were important; for, though the experiments so far noted did not decide just how the oxygen was used in the cheese-whether it was taken up by the fats, the sugar or the caseine-they demonstrated the fact that oxydation was a necessity in curing cheese, and paved the way for more definite knowledge.

Without intending to follow these experimenis through, I have given so much of what was done, because it will be easily understood, and because it will show the origin of the first positive knowledge we have that the curing of cheese is an oxydizing process.

The importance of oxydation in cheese and in curds in the process of manufacture is a new feature in cheese making. It has, it is true, often been noticed by observing dairymen that cheese is improved by airing the curds when they are about ready for pressing, but no explanation was ever given or known as to the cause or the nature of the changes which take place. Its importance is generally supposed to consist in cooling. Though it is always interesting to know how any valuable discovery originated, to the public it is of much less consequence than the fact of the discovery itself and the use which can be made of it.

For the last two years, and particularly for the past year, I have been studying up the significance of the facts developed in the University, and have found that the oxygen is largely taken up by the fats; that under the influence of the rennet used in curding the milk the oxygen combines more readily than it otherwise would with the carbon of the fats, forming carbonic acid gas and liberating heat and water, leaving a

residuum always differing in flavor and odor from the original fat and with a greater levity. I have traced this oxydation from the cheese in the curing room through all the changes of the curd in manufacturing, and in the milk back to the time it came from the udder, and even before, and found it to be the cause of peculiar and increasing odors which develop in warm milk when agitated in confinement and which have erroneously been supposed io come from putrefaction.

To know what agents are at work upon his milk and curds and cheese, is of vast importance to the cheese maker, because it enables him to to know how to counteract or facilitate changes to accomplish desired ends. It makes him master of the situation. It has enabled me during the heat of summer-in July and August-and often out of milk which cheese makers have condemned as unfit for use, to make as good cheese as at any time in the season, and as firm and durable and with as much certainty in results. It has given every cheese maker who has become acquainted with the facts the ability to remove, with ease and certainty, all undesirable odors from his cheese, such as those coming from so-called tainted milk, or from strong flavored or odoriferous herbage consumed by the cows, as the odor of turnips, cabbage, tares, strong weeds, and even leeks—all of which he effects by simply keeping his curds, after dipping, sweet, fine and warm, to facilitate their oxydation and holding them so till the odors are gone. The change in manipulation is but little. The difference comes from knowing what agencies to employ and how to make them available.

The discovery of the part which oxygen plays in the changes of milk, curd and cheese, appears to me to be of more importance than any other event in the hisiory of cheese making, though much that relates to its action is yet to be studied out. This we have reason to believe will be done. The investigation started in 1875, and suspended for some time, has been renewed again, and is now going on with a fair prospect of further developments in that direction.

In conclusion, I will describe some of the leading items which have been adopted to carry out in manufacturing the principles explained. The mode of working now, as I have already said, is different from what it was two years ago, and will be changed further should new discoveries be made, as doubtless there will, for we are yet a great way from perfection in any of the arts relating to the dairy.

CONDITION OF MILK PREFERRED.

Milk for the non-acid process is best when sweetest and newest. Milk of any age, even to incipient souring, is best worked by the new mode,

but it appears that the cheese loses something in solubility by increased age in the milk. The earlier it is worked the higher the flavor, the richer and more digestible is the cheese.

TEMPERATURE FOR APPLYING RENNET.

As rennet acts most rapidly and efficiently at about blood heat, that temperature is preferred when all new milk is to be used. Experience has shown that when milk has been transported, as in transit to factories, and become ten or twelve hours old, if heated to 98° the cream is apt to become oily enough to escape so as to make the whey a little roily. To avoid this I have adopted the rule, when night and morning's milk are to be mixed at factories, of adding the rennet at 90° instead of 98°. Milk which is pretty stale may require a still lower temperature. It is always desirable to shorten the labor of the manufacturer as much as we can, and as rennet acts slower as we go from blood heat down, the general rule I adopt is to set as high as the milk will bear, on account of roiling the whey, and without hurrying the ripening of the curd faster than it can be properly cared for in the earlier stages, as when milk becomes stale. The effect of high or low setting upon the quality of cheese is more imaginary than real.

RENNET AT ITS PREPARATION.

Besides coagulating the milk, rennet affects the curing of cheese. The quantity used should have some reference to that end. For this purpose the quantity which will cause coagulation to become apparent in average. milk in fifteen minutes at about 90° is about right. Milk which is very new will require more to effect coagulation in a given time than when it has stood several hours. As it grows stale it will curdle with less rennet in a given temperature and time, but it is better to use the fullamount and set lower, if necessary, to secure efficient curing.

Rennet extract is always preferred when it can be had. When rennets are used they are soaked with a weak brine-never in whey either sweet or sour. Whey is always stale when separated from the curd and is generally more stale than the milk from which it is derived would have been at the same age. Whey once out of the curd-whatever its condition-has no further business in cheese-making.

CUTTING THE CURD.

I prefer to cut the curd, as cheese-makers would think, rather early and pretty fine. The whey separates more readily and more perfectly when cut early and fine than when left longer and in larger pieces. I

adopt this rule: count the minutes from the time of putting in the rennet till curding first appears, and multiply them by two and onethird, and it will give the best time for cutting. To illustrate, suppose urding begins to appear in fifteen minutes after the rennet is applied, we have 15×235 the number of minutes from the time of putting in rennet to the time for cutting. If the milk begins to thicken in twelve minutes, then it would be ready in twenty-eight minutes to eut, from the time of setting, and so on for longer or shorter curding.

Whether the cutting should be done all at one time or at intervals, and the kind of cutter best to use, are questions which have the same bearings in the sweet curd process as in any other. The operator may suit himself. It facilitates the work to cut right along until it is done, and I like to do so, that the day's work may be as short as possible.

STIRRING THE CURD AND HEATING.

In this operation nothing special is required. What would be best in any other process would be best in this. When it has settled and before it adheres it should be stirred enough to keep it from matting together. As soon as it is firm enough to stir steadily without roiling the whey, say in twenty minutes after cutting, heating begins, and stirring and heating continue till warmed to 98°. As the whey separates more rapidly and perfectly at blood heat, the sooner that temperature is reached the better, but the heating must not be so rapid as to bake on the bottom. The heating and stirring should correspond so as not to heat unevenly. It is not safe to heat more than a degree in two minutes. This would be too fast for the acid process in which it is important to keep the inside and outside of the lumps alike. In the non-acid process, there being no fermentation, the average condition of the curd need only be considered.

DRAWING THE WHEY.

This is done when the curd becomes so firm that when moderately pressed in the hand it will spring apart when the hand is opened. When the whey is once out of the curd the sooner it is taken away from contact with it the better, and I make it a point always to dip as soon as I think I can keep the curd fine by stirring. It must have some solidity or it will pack as soon as the whey is off-but it is never allowed to run till acid becomes apparent.

AFTER TREATMENT OF THE CURD.

As soon as the whey is off, instead of packing in the vat as was formerly done, the curd, in warm weather, is put into a sink with a slatted

rack bottom covered with cloth, and on this cloth it is stirred to keep it from adhering. While in this situation, it is constantly taking in oxygen and giving off carbonic acid gas, and liberating whey and water from its interior. The rapidity with which this goes on depends upon perfect drainage, atmospheric exposure, fineness, temperature, and freedom from acid and salt. In this way the curd is kept lying in the sink, fine and warm, till moisture enough has been separated to give the desired firmness to the cheese, and until the oxydation shall have gone on so far that when its activity is checked by cooling and salting the gas which it occa. sions will not form inside of the cheese faster than it can escape from the curd, so that the pressed cheese shall remain solid and compact. If we fail to carry on this oxydation sufficiently far before pressing, or fail to check it with sufficient salt, or excite its activity by pressing the curd too warm, then the oxydation will be so rapid that it will liberate gas faster than it can escape, and the new cheese will huff and be full of holes. It is a very important item to be able to decide when the ripening has gone far enough to insure a safe and desirable condition in the mature cheese. Experience has developed the following rule: Keep the curd fine and warm (at 90° or above), and thoroughly drained and well stirred till it breaks down, and instead of feeling harsh and rigid, it begins to feel plastic and silky when pressed in the hand, and to have a distinct and cheesy odor and flavor. If there is any strong smell about the curd it must remain till that disappears, or nearly so, before either pressing or salting. If from any cause the curd becomes packed, or forms into lumps too large for the air to penetrate easily, it should be ground as finely as possible, and the airing continued and the grinding repeated, if necessary to keep it fine, till it is properly ripened. Should the mass become too cool, so that the separation of whey ceases too soon before moisture enough is expelled, or its separation too slow, it may be warmed and the work hastened by pouring upon it warm water (from 100° to 120°) till the desired temperature is restored. This will very much facilitate the ripening, and will do no harm. This question of keeping the curd fine all the way through, instead of packing or heaping in the vat, after the Cheddar mode, gives some important advantages. First, it hastens the ripening and shortens the time in getting it ready for the press. Second, it saves all the waste from white whey, as none will occur when the curd is kept fine. Third, it insures a more even salting, because there is little or no variation, from day to day, in the whey retained in the curd, which is not the case when curd is packed on the bottom of the vat. Fourth, it affords a much more complete and ready drainage of whey, which, if retained, would soon sour, to the injury of the curd it might be