130 BOARD OF AGRICULTURE. 



separate tlie fat is not sufficient to prevent the product obtained 

 from heating and destructive changes. If the temperature is 

 raised and the cooking prolonged for a whole day or even longer, 

 the most complete preservation is insured ; and specimens of 

 lard boiled long and with care to avoid burning retain their 

 color, taste and perfect purity for an indefinite period of time. 



I have before referred to the process of canning meats. Tin 

 vessels, to hold eight or ten pounds of meat, are filled, and 

 covers soldered firmly over them. A small aperture is left in 

 the lid according to one process, but in the other the whole is 

 kept tight during the period of boiling in an open water bath, 

 the water of which is heated above 212°, by using a certain 

 quantity of chloride of calcium or other salt in it. When the 

 cans have been cooked for six or eight hours, if perforated, the 

 operator passes round with a cold wet sponge, and, touching the 

 opening, checks the jet of steam. A drop of solder is made to 

 fall on the opening and the process is complete. The cans, 

 bulged by the heated and expanded liquid, collapse on cooling, 

 and the flat ends, being the weakest, yield, whereas the cylinder 

 remains intact. When the lid is not pierced at first, and the 

 meats have been subjected to the action of condensed steam in 

 the tight tin cans, the operator pricks the cover after the boiling 

 is complete, steam flies out, and the opening is promptly soldered. 

 The same collapse of the ends of the cans occurs on cooling. 

 Cans of meat by the million are thus tested in rooms kept con- 

 stantly at a temperature of 90° or 100° Fahr., and but few show 

 signs of change for years afterwards. Heat, the abundant moist- 

 ure within the can, the unaltered organic compounds, remain. 

 Molecules do not form, multiply, aggregate or develop into bac- 

 teria, vibrios or monads. The conditions within the can are 

 conditions which .the chemist or the advocate of spontaneous 

 generation can scarcely deny ought to be favorable to decompo- 

 sition, especially in the testing-room or in the tropics ; but no, 

 the germs of decay have been destroyed, just as they are by the 

 diligent lard and tallow-melter, and five and thirty years even 

 have failed to bring about the molecular aggregation of Bennett 

 and Pouchet. 



Another and very ancient process of meat-preservation consists 

 in cooking meats, sausages, <fec., and enclosing them in well- 

 cooked fats. Dr. Redwood, of London, has used paraffine as a 



