In fact, they are
reciprocal in action. The red yew on the belly of the bow gives the
energy, the sap wood preserves it from fracture. It is, in fact,
equivalent to sinew backing, and though less durable, probably adds
more to the cast of the bows.
In our experiments with a catgut and rawhide backing, we have not found
that they add materially to the cast of a bow, only insure it against
fracture. On the other hand, sap wood and hickory backing materially
add to the power of the implement.
The little red yew bow used in the previous experiment was backed
heavily with rawhide and catgut. It then weighed ten pounds, but only
shot sixty-three yards, showing a decrease in cast. But the backing
permitted its being drawn to ten inches, when it shot a distance of
eighty-five yards. A draw of twelve inches fractured it across the
handle.
In a similar experiment it was shown that two pieces of wood of the
same size, but one being of a coarse-grained yew running sixteen lines
to the inch, the other a fine-grained piece running thirty-five lines
to the inch, the finer grain had the greater strength and resiliency up
to the breaking point, but the yellow coarse-grained piece was more
flexible and less readily broken.
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