GRAIN CONSERVATION 127 



six one-pound tins of pearl barley, part of a lot which 

 had been in store since 1914 and had recently been 

 condemned for weevilling. They were beautifully 

 made tins, soldered with great care, and certainly 

 they looked as if there could not be much wrong with 

 them. One had already been opened, however, and 

 there could be no mistake about the live weevils. 

 The remaining five I plunged into hot water, and, 

 much to my gratification, four of them bubbled at 

 the seams, showing that the soldering was imperfect 

 and they were not really air-tight. The fifth tin, 

 however, appeared to be perfectly sound, and I 

 need hardly say that it contained no live insects. 

 It was quite evident that a weevily sample of barley 

 had been sealed up and that weevils had been able 

 to maintain themselves for four years in some of 

 the tins in which the soldering had been imperfect. 

 It must be remembered that an imperfectly closed 

 vessel, such as a tin can, itself ^' respires," to use 

 a much-abused word in another of its many senses, 

 to some extent like a human being. Changes of 

 temperature and pressure pump air in and out of 

 any small opening, so that the oxygen supply in 

 the interior is constantly being renewed. The same 

 process is responsible for the appalling accumu- 

 lation of dust that takes place in closed drawers in 

 London. The incoming air is laden with dust 

 particles which are deposited before the air is 

 replaced by a fresh dust-laden supply. 



