64 



THE IRRIGA1ION AGE. 



but as far as possible it should be from a 

 driven well. As far as tested, all driven 

 wells of more than twenty-five feet are 

 supplying pure uater. The hard pan near 

 the surface acts as an effective barrier to 

 the passage of germs, and those that come 

 from below are harmless. A driven well 

 of twenty-five feet is a deeper well from a 

 sanitary standpoint than any dug well. 



THE COOLING OP MILK: When first 

 drawn, milk has a temperature of about 

 100 degrees. It will lose part of its heat 

 and come to the same temperature as its 

 surroundings in a longer or shorter period 

 of time, depending upon the bulk and 

 upon the surface exposed to radiation. If 

 left in the lage bulk of the 8 or 15 gallon 

 can, the cooling process is very slow, as 

 there is very little surface from which to 

 lose the animal heat, and nothing to force 

 a continuous and rapid circulation of the 

 milk to the exposed surface. In order to 

 more effectively reduce the temperature of 

 milk, special apparatus has been devised 

 which reduces the bulk to a very large 

 surface for radiation. This is done so ef- 

 fectively that on even small coolers, a 

 pound of milk will spread over 8,000 

 square inches, and from 10 to 30 degrees 

 of heat removed in five seconds. Upon 

 even moderate sized machines, the same 

 can be accomplished in one second. The 

 ordinary 8 gallon can of milk will pass 

 over the cooler in about 12 -or 15 minutes 

 and lose 20 to 25 degrees of heat, while 

 the same if set in a tub of water might re- 

 quire an hour to an hour and a half to ac- 

 complish the same end. 



The effectiveness of a cooler depends 

 upon the area of exposure and the degree 

 of coldness that may be maintained with- 

 in, to abstract the heat. No cooler will 

 abstract more heat than it gives off, so 

 that if 100 pounds of freshly drawn milk 

 passes over it, and it gives up 25 degrees 

 of heat, it will necessitate that 100 pounds 

 of water pass through at 50 degrees. If it 

 is desired to cool the milk more than 25 



degrees, the quantity of water that passes 

 through must be proportionately increased. 

 To cool 100 pounds of milk in a cooler, 

 will require as much water as to cool the 

 same amount in a tub, less the difference 

 in the heat lost from the radiation from 

 the tub during the longer exposure. It re- 

 quires just as much water to cool 100 

 pounds of milk on a small Star cooler that 

 is 17 inches wide and two feet high, which 

 has 1,660 square inches of surface, as to 

 cool it on a Peerless cooler two feet in 

 diameter and two feet high, which has 

 only 520 square inches of surface. The 

 difference will be in the time required. 

 Th ordinary shotgun can present 440 

 square inches for exposure, and the milk 

 can 872 inches, but the layer of milk and 

 water in contact on opposite sides is not 

 changed rapidly. 



DELIVERY OF MILK: Milk is delivered 

 in four ways: (1) by dipping from large 

 cans, (2) by drawing from the bottom of 

 the can, (3) by carrying it in small cans 

 sufficient for each customer, and (4) in 

 glass jars. Each of these methods has its 

 advantages and disadvantages, but the 

 method in most common use is that of 

 dipping. Fully nine-tenths of the milk 

 sold in the city is retailed in this manner. 



The delivery of such a large proportion 

 of the milk by dipping, is the result of 

 habit, and like many others, it is hard to 

 cure. The delivery by means of dipping 

 is the most objectionable of all. In the 

 emptying of a 15 gallon can, the lid is re- 

 moved on an average of 62 times. From 

 our observation there will be four one-half 

 gallon customers, 46 quart customers, and 

 12 pint customers. The lid will be off on 

 an average of more than 30 seconds for 

 each dippiag. taking from 30 to 40 min- 

 utes for each can. By exposure, it was 

 found that this was sufficient time for 

 from 100.000 to 150,000 germs to fall into 

 the can on a dry summer day, and as 

 many as 400,000 on a dusty day. If the 

 lid be made so that it fits into the top of 



