" During this long parenthesis we must not lose sight of the second process of fermentation—viz., the acetous fermentation. We have seen that in the alcoholic fermentation alcohol is formed. In the second process this alcohol is turned into acetic acid, the sour principle of vinegar. In this, as well as in the former case, the ferment is the active principle. Here it causes the alcohol to take up more oxygen and the work is completed. So simple is the change from alcohol to vinegar that it needs but one atom of oxygen to accomplish the transformation, but this can be accom plished only through the action of the ferment. When in the last stage of fermentation, canned fruit or vegetables cannot be saved. If the alcoholic fermentation be detected in time, and the can is heavily exhausted to remove the air and the carbonic ;acid gas, the leak being closed, the can may be saved by the ap plication of severe heat. But the heat must be much more severe than the original process, and the exhaust must be thorough. Such a can will have a not unpleasant alcoholic taste, especially so if the contents be very sweet.
" It may be well to append here some remarks on the effects of swelling upon_ the can-makers' work. The weakest place in a
cylindrical can is the side seam of the body : when cans burst, it is here that the escaping gas generally finds its outlet. When the seam is sufficiently strong to resist the pressure, the cap is the next point most likely to yield. Rarely do we observe a can "burst at the float. When such occurs, it is generally through some defect of the tin. The tin is invariably broken, leaving the rim firmly attached to the body. It is generally observed that when the pressure makes an exit for itself through the can, it is done with such violence, and the evidence of force is so apparent, that it is easy to distinguish a leak so made. It is impossible to confound such a leak with one made by the can maker. The trade is much in need of a machine that will test cans rapidly and efficiently. It seems very crude that we should have to fill a cars and risk its contents before we can tell whether it is good. We should not dare to treat our steam-boilers so. That would be more dangerous, but scarcely more expensive, than the loss on a bad lot of cans."