1919] DAIRY FARMING — DAIRYING. 475 



iug managerial charges. In l'J14 the COSt <>f producing B Quart of milk was 

 4.28 eta and In 1917 it would have been 6.17 eta 



Straining- milk, E. Kki.i.y and J. A. GAMBLE <> . 8. /'«/-/. 1 </' .. Partner? Bui, 



1019 (1910), pp. 24, fit*- 14)~ — Besides a discussion of the significance and 

 sources of sediment In milk and a warning that Btralnlng doea n>>i result in a 

 bacteria-free product, tins publication contains a summary of tests of i in- 

 efficiency of several types of strainers in removing sediment The most efficient 



strainer examined was composed of a layer of absorbent COtton inclosed by 



cheesecloth. Almost equally effective was biter cloth, which can be purchased 



from dairy supply houses and if properly sterilized and cared tor may be DSOd 

 repeatedly. Several thicknesses of cheesecloth have a certain value in remov- 

 ing sediment, but the wire strainer used on 35 per cent of the farms i about 

 40,000) from which reports were received was very unsatisfactory. 



Cooling milk and storing and shipping it at low temperatures, J. A. 

 Gamble and J. T. BowSN {U. S. Dept. Ayr. Bui. V,4 (1919), pp. 28, figs. 21).— 

 The experimental work reported deals with the ellicieucy of cooling devices of 

 various constructions and in different locations and the value of insulation ou 

 cans used for storage and transportation purposes, with special reference to 

 prompt cooling at the farm. The cooling devices dealt with are tanks contain- 

 ing ice ami nonclrculatlng water, into which cans of milk are placed. 



Reports received from some 40,000 dairies in 32 States indicate that about 

 80 per cent of farms producing market milk use some sort of cooling tank. 

 About 1!) per cent of the tanks were of metal, 25 per cent of wood, 31 per cent 

 of concrete, ami 25 per cent of material not specified. Very few tanks were 

 Insulated. 



Cooling in a tank is at an end when milk and water are of uniform tem- 

 peratures. In an ideal tank permitting no absorption of outside heat, the end 

 temperature Is a weighted average of the initial temperatures of water, milk 

 can, and milk, the weights being proportional to the specific capacity of each 

 substance to absorb heat. The measure of tank efficiency proposed is the ratio 

 (expressed as percentage) of this theoretical temperature to the actually ob- 

 served end temperature, the latter always being higher owing to radiation from 

 the surroundings. Directions are given for constructing a concrete tank with 

 insulating substances imbedded in the walls that is 97 per cent efficient. 



Experimental tanks were constructed of uniform size to test the relative 

 ellicieucy of lour different materials, when tanks are either sheltered or un- 

 sheltered from the sun, covered with a wooden lid, or uncovered. Hourly 

 Changes in temperature in the tanks during the progress of experimental cooling 

 are shown by graphs, while the heat absorbed expressed as British thermal 

 units and the relative loss in cooling effects expressed in pounds of ice are 

 given in tables. In the order of increasing ellicieucy the materials used were 

 galvanized iron, solid concrete 4 to 5 in. thick, 1 in. wood not insulated, and 1 

 in. wood lined with 2 in. of cork. The results show clearly the value of a 

 simple board covering and the importance of having the tank indoors, the 

 logical place being the milk house. The added expense of insulation in most 

 cases would soon be compensated for in the saving of ice. In building a tank 

 it is recommended that it be divided into a larger and a smaller compartment 

 so as to allow the economical cooling of different quantities of milk. A tank 

 holding 3 or 4 gal. of water for each gal. of milk is more efficient in the use 

 of ice than a larger tank. "When the water supply is of low temperature, pre- 

 cooling results in economical use of ice and rapid lowering of the temperature 

 of the milk to 50° V. Rapid cooling is also greatly aided by putting ice in the 

 tanks some time before the cans of milk are added. 



