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470 METALS—THE NOBLER.
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under the tongue, the further ends of the metals being then brought into contact together in front.
The
foot-pan, named as illustrating those domestic uses to which Zinc is
commonly put, is one only of many such homely ends which this metal
serves. Vessels of this sort are said to consist of " galvanised iron ;
" which is not the case. No galvanism whatever is employed in their
manufacture ; but they are thinly coated with melted zinc, just as
similar iron vessels are tinned. Zinc in the sheet merely rusts
superficially when exposed to the air and out-door elements, its
substance beneath being thereby protected from any further corrosion.
Because of this reason, the said metal is well-adapted for roofing,
gutter-pipes, and other similar purposes. But on more than one occasion
an outbreak of illness has been reported through rain-water being
washed down from zinc roofing into a zinc tub, and coming into contact
therein with decomposing organic matters, so that a soluble carbonate
of zinc has become formed; which was more or less poisonous to its
consumers.
Workers
in zinc for any length of time get to suffer from spinal nervous
depression, and failure of power, particularly as regards the sensory
functions ; also with a liability to spasmodic affections. These
symptoms arise, of course, from the external effects of the metal
comÂing into frequent contact with the skin, and the mucous linings. A
like result will beneficially occur if metallic zinc is ordained, in a
limited use, for outward therapeutic help against fluxes from the
chest, or the kidneys, and for the profuse night sweats of consumptive
patients. And similar effects may be wrought indirectly by
administering powder of the oxide of zinc in doses infinitesimally
small.
Zinc is the " false silver" of ancient Strabo, and
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