THE COLLECTION AND STORAGE OF ICE. 115 



flowing water is abundant, but the method is not suited for districts 

 in which this is not the case. An attempt was formerly made in 

 North Germany to introduce a method of cold water cooling, which 

 consisted of cooling with water that had been pumped through 

 ice, or with spring water that had been allowed to flow through a 

 suitable ice-house or ice-metre. This attempt, however, has met 

 with little success. 



52. The Collection and Storage of Ice. As the opinion is becom- 

 ing more prevalent every day that ice is indispensable for all the 

 best- equipped dairies, it may be not out of place to add to the 

 description of the ice method given in 50 a few words on the 

 most suitable method for storing ice. 



Very few dairies are in the position of being able to purchase at 

 economical prices the supply of ice they require from day to day. 

 Most of them are forced to lay in for themselves larger quantities 

 of ice, and to keep these for a long time in blocks or in ice-houses. 

 For this purpose, the great difficulty is to minimize, as far as possible, 

 the loss which is apt to take place through melting during warm 

 summer weather. The loss is partly due to the contact of the 

 vessels containing the ice with air, or some solid body which has a 

 temperature above the melting point of ice, but to a far greater 

 extent to the fact that during the warm weather a stream of warm 

 air is constantly passing night and day over the surface of the ice- 

 layers. All spaces in the ice-layer filled with air yield up their heat 

 to the ice, and melt a certain quantity of it. The confined air 

 finally assumes the temperature of melting ice, and becomes of 

 heavier specific gravity than the warm air outside, and tends to sink, 

 owing to its weight, through all the fine pores and crevices surround- 

 ing the lower portions of the ice-heap, outwards, and is replaced 

 by warm layers of air coming in from above and from the sides. 



If ice be preserved in layers, as is commonly done, or in wooden 

 ice-cellars or in wooden ice-houses, it should be surrounded with sub- 

 stances which are bad conductors of heat, and which keep the air 

 from occupying the interstices and pores, besides offering a barrier 

 to the movement of the stream of air. In this way the loss through 

 melting may be largely diminished. If it were possible to prevent 

 absolutely the movement of air over the blocks of ice, the loss would 

 be reduced to a very slight extent, provided the surface remained dry. 



For this reason it is necessary to take precautions to provide a 

 good covering material for the roof. Sawdust, turf, and ashes are 



