ICE-MAKING AND MACHINE REFRIGERATION. 29 



supply to the consumers in our large cities. The provisions, when 

 brought into these buildings, have the temperature prevailing 

 outside, and warm the air that comes in contact with them. This 

 air rises into a loft, where it comes in contact with pipes contain- 

 ing cold brine, becomes chilled, and descends through flues to the 

 room below, entering it near the floor. This circulation goes on 

 until the provisions have been cooled down to the temperature of 

 the room. The air may be cooled, also, without the use of brine, 

 by letting it come in contact with the coils in which the ammonia 

 expands. Air has also been used direct for the production of cold 

 by compressing it. Like condensed ammonia, it takes up much 

 heat in expanding to its ordinary volume, but this system is not 

 economical. In Fig. 5 a somewhat different arrangement is rep- 

 resented. "Where there is not space for the loft, the expansion 

 coils may be placed in the same room with the provisions. Before 

 refrigerating machines came into use, refrigeration on the large 

 scale had been tried with ice, and had failed. This was owing to 

 the dampness imparted to the air by the melting ice. The brine 

 or ammonia coils not only do not add any moisture to the air, 

 but even withdraw a great deal that it naturally contains. This 

 moisture becomes condensed on the pipes as the air circulates 

 around them, and makes itself visible as a gleaming white coat- 

 ing of hoar-frost. On board steamers, machines are employed 

 both to preserve dressed meat and to prevent live cattle trans- 

 ported through tropical regions from dying of the heat in their 

 confined quarters. Machines of moderate size also find applica- 

 tion in hotels two of the recently built houses in New York have 

 them in dairies, chocolate factories, and they are used also in 

 making stearin and margarin, in rectifying alcohol, extracting 

 paraffin from petroleum, etc. A machine of the size represented 

 in Fig. 2 will produce a refrigerating effect equal to that obtained 

 by the consumption of two hundred and twenty tons of ice a day, 

 or it will make one hundred and thirty tons of solid ice daily. 

 The company that makes this style of machine is now building 

 one of three hundred tons refrigerating capacity, which will be 

 the largest in the world. But that is soon to be exceeded, as the 

 contract is already made for a five-hundred-ton refrigerating ma- 

 chine. 



Artificial refrigeration has also been applied to sinking shafts 

 and driving tunnels through quicksand and loose wet gravel. 

 These materials wash into an excavation as fast as they are re- 

 moved, and in many cases progress through them is next to im- 

 possible by ordinary methods. The difficulty is overcome by 

 freezing the loose soil around or in front of the work. This 

 process was first used by a German mining engineer in 1883. In 

 sinking a shaft, pipes of about eight inches diameter are driven 



VOL. XXXIX. 4 



