Page:Popular Science Monthly Volume 3.djvu/482

468 America or Europe has the honor of the invention we need not dispute here. It is now made in this country by thousands of gallons daily, and its manufacture may be witnessed on a large scale at Aylesbury.

Although the process of evaporating milk may be regarded as an exceedingly simple one, the attempt to carry it out at Aylesbury on a large scale has developed a complicated machinery in which steam-power is extensively used; 200 persons are employed, and the milk of 1,200 cows, each yielding 14 quarts, is daily evaporated. The milk used is brought from farms in the neighborhood in ordinary tin cans. Each can before it is sent to the factory is carefully tested by the taste and smell and the lactometer. Any doubtful specimens are set aside for reexamination or rejection. The milk is then passed into a vacuum pan, and the vapor thus produced is carried off and condensed and thrown away. When the milk has acquired a proper consistence, it is mixed with sugar. This addition of sugar is the distinguishing feature of the condensed-milk process. After this the milk is still further condensed till it reaches the required consistence, and is run off into the little tin cans which are so well known. The whole of these operations are carried out with a regard for cleanliness which would look almost fastidious if it were not known that a single particle of decomposing milk allowed to get into the receiving-pans might destroy the whole mass. Every can is returned thoroughly cleansed to the farmer who sends it, having been first submitted to hot water, then to a jet of steam, and then rinsed out by a jet of cold water.

The condensed milk thus prepared is of a semi-liquid consistence, and can be taken out of a jar with a spoon. Several analyses of this milk have been made. The late Baron Liebig found that it contained––

From these analyses it will at once be seen that the only perceptible difference between condensed milk and ordinary milk is, that the former contains more sugar and less water than the latter. Both these things are necessary for attaining the objects for which condensed milk is manufactured. The diminution of the bulk of the water from 87 per cent, in ordinary milk to 25 per cent, in the condensed secures diminution of the bulk of the milk, and thus renders transportation