THE PASTEURIZATION OF MILK 



one due to the temperature of the heated milk will 

 move the pen and cause it to make a proper rec- 

 ord. The same effect may be produced in another 

 way. In this case the compensating coil is con- 

 structed of two different metals, and the differences 

 in expansion cause it to move, but in a direction 

 opposite to that produced by the ether coil. 



It must also be borne in mind that the recorder 

 does not register absolute temperatures, but only 

 relative changes in temperature. Thus inaccurate 

 adjustment of the arm may produce a record which 

 is deceptive. For this reason it is necessary to 

 provide some means of adjusting the arm in order 

 to secure an accurate reading. In some instru- 

 ments the arm has a flexible joint which can be 

 moved by hand. This is rather difficult to accom- 

 plish, without danger of breaking the recording 

 arm, and fine adjustment is not easy. There is 

 also the danger that the joint will be uninten- 

 tionally moved when placing the chart upon the 

 face of the dial. 



In one recorder a post is so placed that it can 



be turned by means of a clock key. After the 



proper adjustment has been made, the post may be 



held in proper position by sealing it to other rigid 



146 



