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Bows

An Experiment on Bow Strings

An English bowstring made of sixty strands of Irish linen, Barbour's number 12, weighs three-quarters of an ounce. The diameter, when well waxed, is ⅛ of an inch; length, 5 feet 8 inches. Each strand of thread has a tensile strength of 6 pounds, or the entire string has a breaking point of 360 pounds. A Negrito string made of some compact vegetable fiber, 6 feet long, ⅛ of an inch in diameter, weighs three-quarters of an ounce.

A comparative test of bowstrings was made with strands of linen, silk, and catgut. Pieces of each of these substances, having a universal diameter of 250 microns, averaged the following breaking points:

Linen thread . . . . . . . . . . . . . . . . 6pounds
Silk thread . . . . . . . . . . . . . . . . . pounds
Catgut . . . . . . . . . . . . . . . . . . . . 4pounds
Cotton thread . . . . . . . . . . . . . . . pounds

Combining five of these threads into one string gave the following breaking points:

Linen . . . . . . . . . . . . . .. . . . . . . . 30pounds
Silk . . . . . . . . . . . . . . . . . . . . . . . 24pounds
Catgut . . . . . . . . . . . . . . . . . . . . . 22pounds
Cotton . . . . . . . . . . . . . . . . . . . . 18pounds

Waxing the threads did not increase their strength. Its use seems to be to keep the fibers from fraying; to reduce the diameter, thus cutting down air friction, and to protect the fibers against moisture.

Catgut soaked in water loses its tensile strength. Catgut of course is only the elastic and fibrous tissues from the submucous coat of sheep intestines. It is iden­tical with the sinew of tendons. Sinew strings do not hold their length under tension, but stretch perceptibly, and are very susceptible to moisture. Cotton stretches under strain. Silk deteriorates when dyed, with age, and when exposed to sunlight. Linen is more durable than silk, and never stretches after it is once put on the bow. It is by far the best material for bow strings. Many substances have been tried to size or stiffen strings, but nothing seems so good as wax having a small proportion of resin.

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