ECONOMIC WOODS OF THE UNITED STATES 63 



shape and size of the stick, and also with the kind and condition 

 of wood. Not only can sound be produced by a direct blow, 

 but a thin board may be set vibrating and be made to give a tone 

 by merely producing a suitable tone in its vicinity. The vibra- 

 tions of the air, caused by the motion of the strings of the piano, 

 communicate themselves to the board, which vibrates in the 

 same intervals as the string and reenforces the note. The note 

 which a given piece of wood may emit varies in pitch directly with 

 the elasticity, and indirectly with the weight, of the wood. The 

 abihty of a properly shaped sounding-board to respond freely 

 to all the notes within the range of an instrument, as well as to 

 reflect the character of the notes thus emitted {i.e., whether 

 melodious or not), depends, first on the structure of the wood, 

 and next on the uniformity of the same throughout the board. 

 In the manufacture of musical instruments all wood containing 

 defects, knots, cross grain, resinous tracts, alternations of wide 

 and narrow rings, and all wood in which summer and spring 

 wood are strongly contrasted in structure and variable in their 

 proportions are rejected, and only radial sections (quarter-sawed, 

 or split) of wood of uniform structure and growth are used. 



" The irregularity in structure, due to the presence of relatively 

 large pores and pith rays, excludes almost all our broad-leaved 

 woods from such use, while the number of eligible woods among 

 conifers is limited by the necessity of combining sufficient strength 

 with uniformity in structure, absence of too pronounced bands 

 of summer wood, and relative freedom from resin. 



''Spruce is the favored resonance wood; it is used for sounding- 

 boards both in pianos and violins, while for the resistant back 

 and sides of the latter, the highly elastic hard maple is used. 

 Preferably resonance wood is not bent to assume the final form; 

 the belly of a violin is shaped from a thicker piece, so that every 

 fiber is in the original in as nearly an unstrained condition as possi- 

 ble, and therefore free to vibrate. All wood for musical instruments 

 is, of course, well seasoned, the final drying in kiln or warm room 

 being preceded by careful .seasoning at ordinary temperatures 

 often for as many as seven years or more. The improvement of 

 violins, not by age, but by long usage, is probably due, not only 

 to the adjustment of the numerous component parts to each 

 other, but also to a change in the wood itself; years of vibrating 

 enabling any given part to vibrate much more readily." * 



* Roth, F., Timber, Bui. 10, U. S. Div. For., pp. 24-25. 



