LACTOMETEES. 



217 



the surface is not level, but, in consequence of the adhesion of the 

 milk to the glass, forms a curve (Fig. 21). There is no difficulty, 

 however, in ascertaining the extension of the curve sufficiently 

 near, and this has to be allowed for in reading off the specific 

 gravity. When using instruments of ordinary size, the curve 

 will be found to extend to about one-half degree. 



Lactometers indicate the exact 

 specific gravity at a temperature of 

 60° F. It is, therefore, necessary, as 

 soon as the position of the lactometer 

 has been noted, to remove the instru- 

 ment from the milk, immerse a 

 thermometer, and ascertain the tem- 

 perature. 



If the temperature is found to be 

 &f F., the observed specific gravity is 

 correct,, but should the temperature of 

 the milk be higher or lower than 60° F., 

 the specific gravity must be corrected 



Fig. 20. — Glass Jar. 



Fig. 21. — Lactometer in J NIi lk. 



by the aid of the Table in the Appendix, which is used as follows : 

 — Find the temperature of the milk in the uppermost horizontal 

 line, and the observed specific gravity in the first or last vertical 

 column ; in the same line with the latter, and under the tem- 

 perature, is given the corrected specific gravity. For example — 

 Supposing the temperature to be 51° and the specific gravity 



