104 



Scientific Proceedings, Royal Dublin Society. 



base line at which the yiekls cease, the spaces between any two joining lines will 

 indicate by how much the yields in lactations of different lengths should differ. 

 According to the diagram, from which the calculation can be made, the yields 

 for an eleven-month lactation should be about 20 gallons below, and those for 

 thirteen-, fourteen-, and fifteen-montli lactations about 35, 65, and 90 gallons above, 

 that for a normal lactation. 



The next and last table, constructed from the Ayrshire Eeports of 1913, 1919, 

 and 1920, gives the average yields of three- to eight-year-old cows in eleven-, 

 twelve-, thirteen-, fourteen-, and fifteen-month lactations. Groups containing 

 yields of less than thirty cows are omitted. The first column in every set of 

 these columns gives the number of cows, the second their average yield in gallons, 

 and the third the decrease (-) or increase ,(-i-) over the average yields in the normal 

 lactation period of 12 months. 



Length of Lactation Period. 



These results are in fair agreement with those inferred from Mr. Gavin's data, 

 and the truth may be taken to be somewhat near them, 



