41 



rugated surface which compels the -milk to run in 

 the little gutters and increases the cooling surface. 

 Also in P the partitions which turn the current of 

 the water which flows as the arrows show on the 

 exposed part of the sketch. The milk flows, of 

 course, in the opposite direction and on a length of 

 8 feet, 2 inches drop is fully enough; indeed, they 

 may be placed nearly level. 



Where they are not desired to be used as con- 

 ductors as well as coolers they may be arranged 

 zigzag as shown in Fig. 34. 



In a trial I made, 22 feet of this cooler reduced 

 900 Ibs. per hour from 156 to 102 with the cool- 

 ing water 74, and' the next 20 feet reduced 

 it to 55 with water circulating over an am- 

 monia coil (about 90 feet, 1 inch) which kept the 

 water at 50. 



Mr. Barber makes these double width to order 

 for pasteurizing purposes. 



Numerous other surface coolers have been de- 

 vised, but these are the principal ones. 



COOLERS WITH PROTECTED SURFACE. 



Cross Section NM While I feel inclined from a practical stand- 



Fig 43 point to overlook the demand of bacteriologists for 



a heater with covered surface, I am more inclined 

 to acknowledge the value of protection against the air during cooling, 

 especially the last cooling. 



Prof. Russell suggests the one shown in Fig. 44. It consists of 

 two tin cylinders with only J-inch space between each other, and here 

 the milk flows through (MC). The cylinders can be taken apart at 

 one end and inlet and outlet pipes can easily be removed by "a ground 

 joint like an ordinary sink plug". They are submerged in a tank which 

 is filled with water, which also passes through the inner cylinder as 

 indicated in the illustration. 



With this cooler and cold water the milk can be reduced from 25 

 to 40, says the professor. 



I have shown how Hochmuth and Lawrence protected the milk 

 against the air by a mantel, and now illustrate how the exacting Prof. 

 Bitter protected the cooler shown in Fig. 42 by a cover B (see Fig. 45), 



