These facts are readily explained by considering, that the action of heat
retained by the silver vessel so far exhausts the herb as to leave very
little soluble substance for a second infusion; whereas the reduced
temperature of the water in the earthenware pot, by extracting only a
small proportion at first, leaves some soluble matter for the action of
a subsequent infusion.
The reason for pouring boiling water into the tea-pot before the infusion
of the tea is made, is, that the vessel being previously warm, may
abstract less heat from the mixture, and thus admit a more powerful action.
Neither is it difficult to explain the fact why the infusion of tea is
stronger if only a small quantity of boiling water be first used, and more
be added some time afterwards; for if we consider that only the water
immediately in contact with the herb can act upon it, and that it cools
very rapidly, especially in earthenware vessels, it is clear that the
effect will be greater where the heat is kept up by additions of boiling
water, than where the vessel is filled at once, and the fluid suffered
gradually to cool.
When the infusion has once been completed, it is found that any further
addition of the herb only affords a very small increase in the strength,
the water having cooled much below the boiling point, and consequently,
acting very slightly.
_Ibid._
* * * * *
THE NATURALIST.
* * * * *
THE HUMAN EAR.
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