468 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



meltiii;^ had moistened aud injured the fish. The ice, it was said, couhl 

 not keep the fish more than a aionth, whereas, by the new method they 

 couhl be kept for years if need be. Tije apparatus used is described 

 as a box in which the fish are i)hiced in small quanities on a rack ; the 

 box has double sides filled in between the sides with charcoal or other 

 nonconducting material. Metallic pans filled with ice aud salt are set 

 over the fish and a cover shut over the box. About twenty-four hours 

 were required to conqdete the freezing, the freezing mixture being re- 

 uewed once in twelve hours. "The fish may afterwards be coated with 

 ice by immersing them in iced water or by applying the water with 

 a brush. They may then be wrapped in cloth and a second coating 

 of ice applied, or they may be coated with gum-arabic, gutta-percha, 

 or other material to exclude the air and to prevent the juioe« from es- 

 caping by evaporation. " The fish are then packed closely in a pre- 

 serving box, which is without a cover, but within a covered box, the 

 space between the boxes being filled with charcoal or other non-con- 

 ductor. Metallic tubes pass through the inner box for the introduction 

 of the freezing mixture, a small pipe connecting with the lower end of 

 the tubes to carry oft' the brine. The combined area of the tubes is re- 

 quired to be one-fifth the area of the inner box in order to keep the 

 temperature below the freezing-point. 



Numerous and complex methods offish-freezing have been invented 

 aud more or less practiced since Mr. Piper obtained his patent. The 

 latest improvements are the sinq)lest and perhaps the most effective. 



In 1869 Mr. William Davis, of Detroit, patented a freezing-pan for 

 fish, which he describes as a thin sheet-metal pan or box, in two sections, 

 one made to slide over the other, the object being to place the fish or 

 meat in one section or part and to slide the other part over it aud in 

 close contact with the articles to be frozen. The boxes are then to be 

 piled in a large close wooden box, the double sides of which are filled in 

 with charcoal or other non-conducting nuiterial. Ice and salt is packed 

 over and about the metal pans. In from thirty to fifty miiuites the con- 

 tents are frozen solid and may be taken from the pans and packed in the 

 keeping chand)er, where the temperature is constant at G'^ to 10° below 

 the freezing-point. 



Mr. Davis in the same year obtained another patent for a pfeserviug 

 chamber, which he says may be a room or box of any desired form. It 

 has double walls, with the intervening space filled with a non-conduct- 

 ing substance. Within this are metal walls of less length thiiu the out- 

 side walls, so that between the two a freezing mixture may be placed. 

 Entrance is obtained through the top or side by closely-fitting doors or 

 hatches. 



Other meihods have been practiced, such as putting the fish in rub- 

 ber bags or in other waterproof material and jiacking them in ice and 

 salt. One method is described as a series of circular pans, seven in num- 

 ber, of such dimensions as to fit in a barrel, and in these pans the fish 



