DAIRY. 135 



2d. In a state of repose and in a cool tempera- 

 ture, this oily matter separates itself, in a great de- 

 gree, from the serum and curd, mounts to the sur- 

 face, and there forms a pellicle of greater or less 

 density. 



3d. When in contact with atmospheric air, it 

 draws from it a portion of oxygen, and thence ac- 

 quires a yellow colour and a disposition to harden. 



4th. Agitation and pressure are necessary to sep- 

 arate it from the serum and curd which may have 

 mounted with it. And, 



5th. To correct its tendency to decomposition, 

 which first shows itself by a rancid smell and taste, 

 it must be subjected to the action of heat, or a por- 

 tion of the muriate of soda must be incorporated 

 with it. From this theory of butter-making, it will 

 be easy to deduce the rules necessary to practice. 



1st. The formation of cream is, as we have seen, 

 a process of nature which we best promote by giv- 

 ing to our dairies a northern exposition ; by keep- 

 ing them perfectly clean ; because filth, besides other 

 mischief, is predisposed to fermentation, and is, of 

 course, productive of heat; and, lastly, by so form- 

 ing our pans as to make them narrow at the bottom 

 and wide at the top, to the end that they may offer 

 to the atmosphere the largest possible surface.* 



3d. The separation of the butter from the milk, 

 with which it is still connected, is our own labour, 

 and must be carefully and thoroughly performed. 

 This is called churning, and ought to be only a mod- 

 erate and continued agitation. If the movement be 

 too slow or frequently interrupted, the effect intend- 

 ed is not produced ; and if hurried and violent, the 

 cream is too much heated, and yields a white and 

 curdlike butter. When this operation is well per- 

 formed, the butter is found adhering to the staff and 

 flyers 'of the churn, is of an agreeable taste and col- 

 our, and of a certain degree of consistency. 



* See, in Fourcroy's Chymistry, vol. ix , the effects of cover- 

 ing milk-pans. 



