72 SCIENCE AND PRACTICE OF DAIRYING. 



as near 15 C. as can be obtained. The depth of the cream layer 

 is noted for the purpose of calculating its percentage volume, after 

 which it is removed. The specific gravity of the skim-milk at 

 15 C. is then determined, so that it may be seen whether it remains 

 within the usual limits. This method has been found extremely 

 useful for testing milk suspected of having been creamed and 

 watered, especially in hilly districts, where the conditions of milk 

 production do not exhibit such wide variations as are often found 

 in some districts of flat lands. 



The "byre -test" furnishes a complement to this formerly 

 largely-used method of milk-testing. 



The byre-test is carried out in the following manner. If, on investiga- 

 tion, a sample of milk of known origin is found to yield unusual results, the 

 byre is visited as soon as possible and the milk investigated. The results 

 thus obtained are compared with the previous ones, so that it may be 

 ascertained whether the earlier results are confirmed. Where the results of 

 the byre-test are to be given as evidence in a court of justice, the test 

 must be carried out in the presence of witnesses, and care should be taken 

 that the cows are thoroughly milked. It is advisable, therefore, that a 

 skilled milker should be employed, or that the operation should be carried 

 out under his directions and to his satisfaction. The quicker the byre-test 

 follows upon the seizure of the sample of milk, the more valuable are its 

 results for purposes of proof. The same milking-time as that at which 

 the suspected sample was obtained should be chosen, as well as the same 

 cows which have been milked, and the test, if possible, should be applied 

 within 24 hours, and in no case should more than three days be allowed 

 to elapse. It is necessary generally to submit the milk coming from the 

 whole of the cows in question to investigation. In this way the milk of 

 each single cow can be tested. If no important change in the feeding 

 and treatment of the cows have taken place in the interval between the 

 time of the milking of the suspected sample and the milking of the sample 

 taken for the by re -test, then the duplicate results, in the absence of 

 adulteration, should show a variation of not more than a two-thousandth 

 in specific gravity, equivalent to a difference in fat of not more than 

 3 per cent, and a difference in the total solids of not more than 1 per 

 cent. Where larger variations than the above are found, then the sus- 

 picion of adulteration is confirmed, and in some cases may be absolutely 

 proved. Caution must always be exercised, however, since it has been 

 noticed occasionally in very few cases, it is true that the specific gravity 

 of the milk of single cows has shown a difference, from day to day, of 

 several thousandths, indeed, as many as six, and a difference in the 



