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178 HISTORY OF DENTAL SURGERY
shrinkage or expansion by specific gravity, and also made experiments with
various percentages of gold in silver-tin alloys.
Kirby (Transactions of the Odontological Society, Great Britain, 1871-3),
made use of a V shaped trough in which to make fillings and measured con-
traction or expansion with a micrometer screw. Another test, for expansion
only, was by making fillings in very thin glass tubes wliich were split by expan-
sion. Dr. Thomas B. Hitchcock, of New York (Transactions of the New York
Odontological Society, 1874) made fillings in a steel trough an inch long
which he measured within 1/1000 of an inch by means of a lever with very
short and very long arms. He tested about a dozen amalgams, but died before
his results were completed, and publication was made from his notes by Dr.
E. A. Bogue. Some experimental work was done in France and Germany, but
it was mostly of a similar character. Dr. Adolph Witzel, however, tested fill-
ings of known composition which had been worn in the mouth for some years
by sawing through fillings and tooth, jjolishing and examining with a micro-
scope.
Much was written about amalgams, especially by J. Foster Flagg, but it
was mostly from a clinical standpoint and gave too little of accurate observa-
tion to be of scientific use. As a result of these various experiments three
plans of measurement for shrinkage or expansion liad been shown to be
possible. First, by t!ie microscope, examining fillings made for the purpose,
by John Tomes; second, by the specific gravity test, by Charles S. Tomes;
third, by a micrometer, by Thomas B. Hitchcock.
Great search had been made among possible metals for amalgam alloys
and it had been conclusively sliown that silver and tin must serve as the basis
of them, no others proving usable in large proportion.
Some good resulted from thege numerous efforts and experiments, and it is
possible that if Dr. Hitchcock had lived, the main facts about amalgams might
have been discovered a quarter century sooner. Notliing really decisive was
accomplished till, in 1895, Dr. G. V. Black set himself systematically to the
task of solving the amalgam problem.
It soon became apparent that most of the tests for shrinkage or expansion
were either very unreliable or very inadequate. For instance, it was easily
proved that the changes from d
shrinkage or expansion in blocks of ivory, or in extracted natural teeth, than
ever occurs in any amalgam. This implies, of course, that if these are used
for making test fillings tliey must be kept all the time saturated with
