698 APPENDIX A 



evaporation of the refrigerant takes place in coils over which 

 a current of air from the chamber or chambers is carried by 

 means of a fan, and in the passage the heat is absorbed by 

 the refrigerating gas expanding in the coils. 



The technical details of the application of refrigeration to 

 dairy practice is a wide subject and cannot be adequately 

 dealt with here, but during the last few years it has attained 

 such prominence that it is necessary for those who are 

 interested in the business that they should realise its great 

 importance. 



The Alfa-Laval Centrifugal Cream Separator, the in- 

 genious invention of Dr de Laval, 1 came from Sweden, and was 

 exhibited at the R. A. S. Show at Kilburn in 1879. Within 

 twenty-seven years no implement has made greater progress 

 in efficiency and in popularity. Its working capacity has 

 been thrice nearly doubled: first, in 1891, by reducing the 

 size of the formerly large hollow revolving steel bowl, and 

 nearly filling with a series of cone-shaped " Alfa " discs, by 

 which the milk is divided into thin layers and cream separa- 

 tion greatly accelerated ; second, in 1900, by introducing the 

 supply at that area of the revolving discs where the specific 

 gravity of the milk is normal ; and third, in 1906, by strengthen- 

 ing and detaching the spindle and raising the upper end of it 

 upon which the bowl rests, above the centre of gravity of the 

 bowl when full of milk. This reduces the vibration so much 

 that the saving in the driving power is enormous. The work 

 of separation now begins at once, and is not retarded in its 

 progress by either cream or separated milk coming in contact 

 with the supply of in-coming milk, as was formerly the case. 



The second improvement which brought this about was 

 invented by an American. Since 1891 the speed of the bowl 

 has been reduced from 7000 to 5600 revolutions per minute, 

 and the cost of driving irr^imilar proportion. The percentage 

 of fat left in the milk since these advances is only -03 to -08 

 per cent. Professor Stokes, P.A., Paddington, reported on a 

 sample of milk separated by the " new model " machine as 

 follows : " It contains only one-fourth of the amount of 

 butter-fat usually left in by separators. It is the smallest 



1 Acknowledgments are due to the article, " History of Agriculture," by 

 the present writer, in HarmsivortWs Rncyclopcedia. 



