468 THE POPULAR SCIENCE MONTHLY. 



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 feat- 

 ure 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 opera- 

 tions are carried out with a regard for cleanliness which would look 

 almost fastidious if it were not known that a single particle of decom- 

 posing 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 Ween made. The late Baron Liebig found that it contained 



Water ....... 22.44 



Solids ...... 77.56 



100.00 



The Lancet has more recently published the following analysis : 



Moisture ...... 25.10 



Butter ...... 11.73 



Caseine ...... 15.17 



Milk-sugar . . . . . 16.24 



Cane-sugar ...... 29.46 



Ash . . . . .' 2.30 



100.00 



From these analyses it will at once be seen that the only percep- 

 tible 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 



