Benton — Properties of Catgut Musical Strings. 383 



Art. XXXIX. — The Mechanical Properties of Catgut Musi- 

 cal Strings y by J. R. Benton, Ph.D. 



The experiments here described were made in connection 

 with investigations on the stress-strain relation in elastic solids, 

 carried out at the Geophysical Laboratory of the Carnegie 

 Institution under the direction of Dr. G. F. Becker, to whom 

 the writer desires to make acknowledgment for many valuable 

 suggestions in regard to the work presented in this note. 

 Researches on the stress-strain relation have been made for 

 rubber and for the metals ; and it was thought of interest to 

 experiment also on a substance of intermediate properties as 

 regards extension within the elastic limit ; for this purpose, 

 catgut, as used for strings of musical instruments, appeared to 

 be best adapted. Owing to its hygroscopic properties and the 

 complicated nature of the after-effects it exhibits, it was found 

 that a precise determination of the deviations from Hooke's 

 law would involve an amount of labor far greater than was 

 thought to be warranted by the importance of the substance. 

 Such results as were obtained, however, together with general 

 data on the mechanical properties of catgut, seem of sufficient 

 interest to justify the publication of the present note. 



Tensile Strength. — A piece of catgut -061 cm in diameter had 

 an average breaking load of 12'0 kg., corresponding to a ten- 

 sile strength of 43 kg. per mm 2 (60,000 lbs. per sq. in.). A 

 piece *038 cm in diameter broke under 4*5 kg., corresponding to 

 a tensile strength of 41 kg. per mm 2 . These figures show that 

 it is nearly as strong as copper wire, and must be classed as 

 one of the strongest organic substances, far exceeding all kinds 

 of wood (less than 20,000 lbs. per sq. in.), leather (5000 lbs. 

 per sq. in.), and hemp ropes (15,000 lbs. per sq. in.). 



Catgut musical strings, as furnished on the market, are 

 twisted, and tend to untwist when subjected to tension, and to 

 twist up again when tension is removed. In order to study 

 their elasticity, this twist must be removed, which is accom- 

 plished by soaking the string in water. If hot water is used 

 the string becomes very soft, and contracts greatly in length. 

 In this condition it behaves very much like rubber ; it can be 

 stretched to nearly double its unstrained length, and when 

 released it snaps back like a rubber band. 



It is greatly weakened, however, by being wet ; but it 

 regains its strength more or less completely upon drying, as 

 shown in the following table : 



