386 Benton — Properties of Catgut Musical Strings. 



catgut, and humidity (absolute), both as functions of time. 

 After-effects were detected also in connection with change of 

 temperature. 



The elastic after-effect is of course responsible for the beha- 

 vior of new strings on violins, which get out of tune very 

 rapidly at first, and always in the direction of lower pitch. 

 With greater duration of the tension the after-effect becomes 

 less marked and the material approaches equilibrium under the 

 imposed conditions. But if left for some time, the tendency 

 is always towards lower rather than higher 

 pitch, if temperature and humidity do not 

 2 change. 



To protect the string from changes of humid- 

 ity, it was placed inside of a tube of galvanized 



( ) iron ( u spout-pipe "), 6 inches in diameter, and 



<) 



a. 



2 meters long, 



the seam of which was soldered 

 up (&, fig. 2). Near the top and bottom, plate 

 glass windows (b, &), 7|-Xl5 cm , were fastened 

 into it and made moisture-tight by liberal appli- 

 cation of thick grease ( a mobilubricant ") be- 

 neath the glass and around its edges. Inside 

 the bottom of the tube a circular trough (o, fig. 

 2) 4 cm wide was soldered against it and filled 

 with engine oil. A hanger was attached to the 

 bottom of the catgut, and hung through the 

 hole in the middle of the trough ; to this 

 hanger was fastened an inverted cup (a) of tin, 

 which dipped into the oil of the trough. Thus 

 the catgut was completely protected against 

 changes of moisture in the air, and at the same 

 time could be subjected to any desired tension 

 by placing weights upon the hanger sticking 

 out from the bottom of the tube. The whole 

 arrangement was supported from the ceiling 

 and braced against the floor. Micrometer tele- 

 scopes for reading at top and bottom were sup- 

 ported from the tube itself. The top telescope 

 took account of any sinking of the upper sup- 

 port ; the distance between the two marks 

 sighted upon on the string was 138 cm . The tele- 

 scope at the bottom could be shifted bodily to keep up with 

 stretching of the string ; a reflection prism was fastened to it 

 in front of its objective, and reflected into its field of view the 

 image of a steel centimeter scale fastened vertically near by. 

 In this way the shift of the telescope when moved could be 

 measured. 



Coefficient of Thermal Expansion. — After the catgut had 

 been in the tube four days, readings were made upon it from 



