1881.] on Musical PUch and lis dctcnninatim. 537 



(Umlity, pitch was the most susceptible of accurate measurement, and 

 that the recent great advances in physical science were mainly due to 

 tlio substitution of quantitative for qualitative methods ; of weighing 

 and measuring for mere demonstration. He showed that absolute 

 l>itch did not exist in nature ; a fact not negatived by the remarkable 

 power exceptionally possessed by some ears of recognising a note by 

 hearing. This so-called gift was really an acquirement, depending in 

 some cases on the " muscular sense," as in the case of singers ; or on 

 a development of memory in others who, like organists, had sat for 

 half a lifetime before a particular instrument, until its tones had 

 penetrated into their inmost and instinctive consciousness. It was 

 not dissimilar to the acquired habit of counting "tea/s," which was 

 the foundation of piano- and organ-tuning, and which once established 

 interfered seriously with the pleasure of listening to ordinary music. 

 Examples of these heats and their causes wove shown. 



He proposed, after defining pitch as rapidity of vibration, to take 

 three questions in succession : (1) the chief causes, and amount of 

 variation in pitch in different sound producers ; (2) scientific modes 

 of measuring pitch ; (3) the musical application of such methods, 

 carried a stage farther in an artistic direction than was usual in 

 treatises on acoustics. 



It was shown experimentally that a metallic string through which 

 a powerful current of electricity passes sinks more than an octave in 

 pitch ; that a tuning-fork heated over a lamp also sinks in pitch, 

 though to a far less degree ; that organ pipes vary greatly with heat, 

 and also with watery or other vapour, rising rapidly with increased 

 temperature. An instrument for measuring this phenomenon, made 

 by the Lecturer, was shown. In it air from the same wind-chest was 

 passed through two coils of metal pipe, one maintained at the tempe- 

 rature of melting ice, the other at that of boiling water. Rapid and 

 distinct beating was thus produced in two pipes previously tuned to 

 imison. Harmonium reeds moved in the same direction as tuning- 

 forks, though in a greater degree ; the former sinking about one 

 vibration in 10,000 for each rise of a degree Fahrenheit, the latter 

 about 1 in 16,000. 



Both these quantities being small relatively to the changes under- 

 gone by other sources of sound, the tuning-fork furnished the best, 

 and the free reed nearly as good a standard of pitch. The reed, how- 

 ever, depended somewhat on its material ; a brass and steel reed on 

 the same wind-chest, and in unison, beating distinctly when the air 

 supply was raised to 212° Fahrenheit. 



In orchestral wind-instruments a double action took place, the 

 metal expanding with heat tending to flatten the note, whereas the hot 

 and moist breath of the performer caused it to sharpen, the latter 

 action greatly predominating in this climate at least. 



(2) The scientific determination of pitch had been attacked by five 

 2inucipal methods. (1) mechanical, (2) optical, (3) photographic, 

 (4) electrical, and (5) computative. 



