In this plant the aeration is conducted by blowing in air at the base of the condenser.
It should be observed that the free acid is gradually neutralized, partly by chemical action on certain constituents of the slime, partly by local action between different metals of the anode, both of which effect solution independently of the current, and partly by the peroxidation (or aeration) of ferrous sulphate formed from the iron in the anode.
But research showed that this process of nitrification is dependent on temperature, aeration and moisture, as is life, and that while nitre-beds can infect one another, the process is stopped by sterilization.
They serve probably for the aeration of the gonads by admitting to their vicinit y water with its dissolved oxygen; they never serve as genital ducts, since the generative products are always dehisced into the stomach and pass out by the mouth.
Again, the well-known action of earthworms may be said to be a biological work; but the resulting aeration of the soil causes edaphic differences; and earthworms are absent from certain soils, such as peat.