Discussion on Mil/i. 
419 
neous view to take to say that excess of air was injm-ious to milk. 
He would recommend that the air should be allowed to penetrate the 
millc and come in contact with it freely. If they could also maintain 
a cm-rent of air tlirough the dairy, it would be all the better ; but 
damp air resting upon the i milk would prove very injurious to it. 
Eecently a little work had been published in Sweden, which recom- 
mended that the milk should be exposed in shallow vessels of a 
peculiar shape and haudy construction which fi-ecly admitted the 
air. A part of the author's iilan was to have a fire in the dairy 
whenever it was required ; and he ^'^■as informed that when a thunder- 
storm was seen approaching, instead of keeping the milk cool, a fii-e 
was at once lighted, and steam got up to drive out the excess of 
moistm-e. That might seem to be a curious proceeding ; but he 
could readily imderstand it. It was the damp, moist, heavy aii' that 
spoiled the milk. Eemove that air by any means, and the milk would 
keep. It is of the utmost importance to have a dry air in the dairy ; 
and they could now imderstand why good dairymen always kept the 
floor as dry as possible. When a thunder-storm approached, the air 
generally became satm-ated with moistm-e, and that moistm-e had a 
great deal to do with spoiling the milk. 
Mr. Blackeuun said he had always foimd that a small depth of milk 
threw up the largest quantity of cream, especially in warm weather, 
when it is important that the cream should be thro-mi up quickly 
because the milk would not keej) long. In summer he invariably 
adhered to a depth of 14 inch, and in winter to one of 4 inches ; and 
the skimmed-milk did not then remain sufficiently long to acquire 
any acidity. He had found that bean-meal produced a greater quan- 
tity of milk than any other kind of food. In comparison with rape- 
cake and linseed-cake, ho found that it contained a larger amount of 
flesh-making principles than those substances, but not so much oil. 
Grains, or draft, also produce a large quantity of milk, which appear 
to contain a large quantity of phosphoric acid. He had fed likewise 
largely with bran. Between linseed and rape-cake there was great 
difl'erence. Linseed-cake gave a very vmpleasant smell and flavom* ; 
whereas rape-cake was more like grass in its effects. The explanation 
might perhaps be, that the oil in rape-cake more resembled the oil in 
butter than that in linseed-cake. 
Professor Voelcker said that bean-meal contained a considerable 
quantity of starch ; it was an admitted fact that it produced a large 
quantity of 1)utter. Grains contained lactic acid, and also a large 
quantity of phosphate of lime, which was held in solution. A certain 
amount of grains is exceedingly useful for dairy-stock, and so also is 
bran. 
Mr. Blackburn further called attention to a plan for testing milk by 
its opacity, or rathoi', the resistance which a body of milk offered to 
the passage of a ray of light, and thus measm'ing it. [Professor 
Voelcker observed that there was such a lactometer ; but it was 
altogether erroneous in principle.] The keeping milk cool is a 
very important point. He had sent a large quantity of milk 
tweuty-five miles by railway, and it arrived in a coagulated state unfit 
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