508 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
boiled they take it out of the brine and are careful not to injure the skin, after which they let it cool 
and drip on a hurdle. Then they expose it for a day or two to the smoke of a fire made of juniper, 
which must make no flame. Finally, they put it into a tin box, the sides of which must be an inch 
higher than the thickness of the fish, and fill up the box with fresh butter, salted and melted. When 
the butter is coagulated they put on the cover and solder it to the lower part of the box. Some persons 
eat the fish without boiling it again, but it is better when it gets a second boiling. In winter good 
oil of olives may be used instead of butter. 
Augilbert’s method, was very similar to the present processes, which differ in some 
minor features, but are uniform iu principle. A definite amount of the article to be 
jireserved, with some liquid, is placed in a tin can, over which the cover, containing a 
minute hole, is soldered, and the can and contents are placed in a bath of boiling 
water. Through the small hole the air and steam escape from the can in boiling, and the 
heat also kills the bacteria. The hole is closed with a droii of solder, and the process" 
of cooking is comiileted. 
A number of modifications and improvements have been adopted, principally in 
reference to shortening the time of cooking, permitting the heated air in the can to 
escape, softening the hones of small fish, filling and handling the cans, etc. 
While it is necessary that the fish be thoroughly cooked, yet in a majority of 
cases it is equally important that they remain as short a time as practicable under 
the action of the heat. This is facilitated by increasing the temperatnre of the 
boiling water. Formerly the cans of fish were boiled in salt water, by which a tem- 
perature of 230° F. is attainable, or in water containing chloride of calcium, or sulphide 
of soda, whereby 250° F. may be secured. But these agents are each prejudicial to the 
metal of the can and the kettle, causing them to rust or wear rapidly, and by using the 
maximum of heat secured by the chloride of calcium process the cans often burst, with 
dangerous effects to the workmen. About 1874, steam-tight cylinders were introduced, 
in which the cans are subjected to a very high temperature by introducing steam from 
adjacent boilers, thus shortening the time of exposure to heat and removing liability 
to burst, the outward pressure in the can being counterbalanced by the inward pres- 
sure of the steam in the cylinder. This was first applied in 1874 in canning oysters. 
At first steam only was used, but it was soon found that the contact of the steam 
with the can results, to some extent, in scorching the contents that lie next to 
the inner surface of the can, and the oysters or fish have a slightly burnt flavor in 
consequence, the can itself also exhibiting a bluish color on the inside. This was 
remedied by placing the cans in water, below the surface of which the superheated 
steam is admitted. The inessure upon the intermediate water is transmitted to the 
outside of the can and counterbalances the pressure from the inside until the cooking 
has been completed. The fish or oysters on the inside of the can are also acted upon 
uniformly by the heat, and neither cans nor contents injured, even if the temperature 
be raised to 250° F. or more. By this process, which has been generally adopted, the 
cooking is done in much shorter time and at greatly reduced expense. 
To remove the air from the can it was formerly customary to leave a minute hole 
iu the lid, heat the can and contents by nearly submerging the can in boiling water, 
and then solder the small hole. At present the cans are hermetically sealed and boiled, 
then punctured to permit the expanded air to escape, when they are resealed, and 
the process of cooking completed. An improved method has been devised, in which 
the air is extracted from the can by means of tubes connecting the tin with a vacuum 
chamber, but it is little used in canning fishery products. 
