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122 THE TREATMENT OF TEETH

plasticity to be obtained without an alternate adding
of mercury and filings. It is this usually adopted
practice, of alternately adding first one, and then the
other of the ingredients, until a mass of the desired
plasticity is obtained, that Dr. Flagg deprecates. He
claims that this will ruin the best amalgams, and
that under proper tests, there is no comparison
between the results obtained by these two methods
of mixing. It is also found that an amalgam made
with one admixture, produces a better plastic mass
with less mercury and the excess of mercury that is
;
often necessary, in order to secure working properties
in an amalgam prepared by the haphazard alternate
mixing method, will transform an excellent amalgam

into a comparatively poor one. (See " Plastics and
Plastic Filling," chap, ix.) The proper method of
mixing an amalgam filling, is to weigh the mercury
and alloy in such proportions, as have been found
upon trial, to make the mass just right for working
in any given case. The balance designed by Dr.
Wheeler, and made by the S. S. White Company,
is a very correct one for this purpose.
Dr. Flagg says :— After determining the propor-
tions of mercury and filings, they are placed in a
mortar, and the filings " gradttally incorporated
with the mercury." " This is done by retaining
the mercury in the centre of the bottom of the