No. 2 (1921) REMARKS ON CANNING 65 



that only warmed air shall enter the room while the fuel gases pass 

 direct into a chimney flue — which may however be of iron and led 

 through the room so as to assist in warming the air — is a good 

 arrangement, but there must be artificial ventilation, such as that 

 of an exhaust fan, or a wide chimney or air flue, supplied with a 

 stove, fire, or large lamp at foot to cause the necessary up-draught, 

 to remove the saturated air. The subject is very complicated and 

 requires a separate treatise with drawings. 



59. In the frying and packing room the chief machine is the 

 frier in which the fish, still in their grilles, are fried in oil at about 

 300° F. in order to drive off some of the moisture from the tissues, 

 and thus ' firm ' the fish which are otherwise liable to break up or 

 'mush' in the cans, and in order to sterilise them prior to pack- 

 ing. This frier consists of a metal vessel containing oil, usually 

 of capacity to take two grilles of fish at a time. The heating of 

 the oil is a difficult matter ; if the oil is heated by direct fire the oil 

 directly in contact with the metal is apt to be unduly heated, 

 giving off acrid fumes by its decomposition, and may easily be 

 scorched by the flames of the fire ; moreover the debris of the fish 

 falls to the bottom of the pan and scorches ; hence the oil rapidly 

 darkens and takes on a burnt flavour which is communicated to the 

 fish so that the oil has to be frequently changed, and this causes 

 considerable expense. Hence various methods to circumvent this 

 difficulty ; since in India open fires will be usual the heat can be 

 modified and equalised by the sand bath method, viz., by placing 

 immediately over the fire a metal trough in which there is a layer 

 of clean sand an inch or so in depth ; the vessel containing the oil 

 is then placed in this sand bath and heated to the desired degree, 

 fairly equally and without undue scorching, since there is no 

 contact with flame. 



60, Instead of a pan over a fire it is common and better to 

 place the furnace at one end of the pan and carry the hot flue 

 gases through horizontal tubes let into the pan and passing 

 through the oil, which is thus heated more equally and with less 

 chance of scorching ; moreover the debris mostly fall between the 

 tubes to the bottom of the pan which is, in this method, the coolest 

 part of the arrangement. This necessitates several roomy tubes 

 and a pan of sufficient length to absorb most of the flue heat. The 

 tubes should be of ////;/ copper which is more conductive of heat 

 than iron and does not oxidize like iron; moreover when worn out 



