590 



EVERYDAY SCIENCE 



specifications of Project XX, a still simpler contrivance is 

 suggested by the Chicago Department of Health. Obtain a covered 

 bucket tall enough and wide enough to hold two quart bottles of 

 milk. For a nest get a still larger bucket that will allow about an 

 inch of insulating air space all around between the nest and the 

 inside bucket. 



To hold this, a covered box at least 14 inches square and 15 inches 

 tall will be needed. Hinge the cover, put a hasp on it, and cleat 



FIGURE 12. 



M, milk in sealed bottles, packed in ice in covered bucket ; S, sawdust 

 packing around nest ; C, hinged cover with newspapers cleated to it. 



to the inside o'f the cover about fifty thicknesses of newspaper, so 

 trimmed that the cover will close tightly. Cover the bottom of 

 the box with three inches of sawdust, lay the nest in the center of 

 the sawdust area and pack sawdust to the top of the nest. A 

 vertical cross section of this box is shown in Figure 12. Use the 

 box as directed in the preceding paragraphs. 



The principle that explains both the fireless cooker and the ice 

 box here described is that a non-conductor of heat is interposed 

 between substances of different temperatures, thus preventing 

 them from equalizing those temperatures. 



N.B. If a tinned iron bucket is used, put a little soda into it each 

 day when the ice is packed. This will tend to prevent rusting. 



