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40 THE TECHNICAL PKOCEDUEES IN FILLING TEETH. ;

the hatchets and hoes are represented by the same formulas.
Take up the hoes, one by one, and lay each beside the hatchet of
corresponding formula ; study the blades in this position. Now
remove the hatchets, one by one, and place them on the second
form, each with the formula on its handle, over the correspond-
ing line of figures. It will be seen now that the hatchets and hoes
are of the same sizes and of the same angles ; there are the same
ranges of sizes and angles. There are in this set, three groups
with blades of equal sizes, with three instruments in each group
also three groups of equal angles with three instruments in each,
of each of the sizes of hatchets and hoes. Each group of equal
sizes has a range of three angles; each group of equal angles
has a range of three sizes, a large, a medium and a small size.
Each blade belongs with a definite class (hoe or hatchet), and
has a definite formula. It will not fit any other.
"When this has been studied, take up the hatchets and jumble
them together, and, looking at the blades only, try naming each
in its turn, laying it in its proper place on the paper on which
the formulas have been written. Do the same with the hoes. Do
this once per day until each blade can be named at sight, as
hatchet 12-5-6, hoe 8-3-23, hoe 6-2-12, hatchet 6-2-23, etc., for all
this set. After this, form the habit of calling each by its full
name. Some will learn these at a single elTort, others may need
as much as five or sis. Then, use of the names will fix them per-
manently in the memory. It is not so much that one may learn
this list of instruments as that he shall learn the application of
formulas to instruments and become able to read formulas from
instrument points or to read the form of instrument points from
formulas. To do this well, he should make many measurements.
THE SPECIALS.
The set of specials are so called because each instrument is
designed for a special use. The formulas of this set are upon a
different set of sizes, or the ranges are on different sizes, the
plan of measurement being the same. In these are also three
size ranges, or widths and lengths of blade. There is, in the
University set, only one angle of blade — 12 centigrades — for
all except the binangled chisels, wliieh are 6 centigrades angle.
The specials present less difficulty in learning to read the
points than the ordinaries, because tliey are in smaller groups
under the class names. They may be studied, however, on
the same plan recommended for tlie ordinaries. These groups,
except the chisels, have each the same or similar ranges under