CHURN, a machine for agitating milk or cream for the production of butter. The principle of the operation is considered in the article on BuTTEn. Of the great variety of forms that have been given to the machine, it is very difficult to determine which deserves the preference. It is obvious that the more thorough and uniform the agita tion, the more completely will the butter be separated from the milk. The consistency and color of the butter are also elements in judging of the relative merits of churns. The temperature of the air and the milk affect the butter in these respects. During summer, that of the milk should not exceed and in very hot weather may be under 6V. During cold weather, the milk should be about 2' higher when put into the churn. The speed at which the operation is performed also influences the result. Trials insti tuted to test the relative merits of churns have failed to settle which is the best form for actual use in the dairy; for the same machine under different conditions does not always yield the same result. The oldest form is the upright or plunge churn. There is a general prejudice in favor of this form of C., on the ground that the butter is more completely separated and of better quality. Its great defect is that the operation, being generally performed by hand, is fatiguing. Recent improvements have chiefly aimed at ease in working, and a saving of time. The original barrel C., with a rotatory motion,
like a grindstone, which motion was reversed every few rounds, has fallen from its once high repute into comparative neglect. An improvement on the barrel C. was the making of the barrel stationary, the milk being agitated by internal apparatus fixed on a hori zontal spindle which is turned by a winch handle. Barrel churns, sometimes of monster size, are generally used in large dairies in Holland. For small or moderate-sized dairies, perhaps the most suitable is the box C., consisting of a cubical or oblong box, of birch or plane tree, having the agitators fixed on a horizontal spindle. Churns on a centrifu gal action have also been successfully used, particularly in Sweden. More recently, churns of a barrel form, with an oscillating motion like a child's cradle, have been intro duced, but without any decisively superior results.
To all forms of churns, power other than manual can be and is applied. In some parts of the continent of Europe, and in America, the dog is employed in churning by means of a contrivance like a squirrel's box. Horse-power is in very general use in large dairies in Great Britain. In very exceptional cases, steam-power is used.