Royal Society. 807 



written at the suggestion of a friend during a Committee held in 

 the Royal Society's Apartments, and, as the concluding words 

 show, was intended to be followed by a more detailed account 

 of the method of observation. The point in question relates to 

 the position of a second slit which was used to screen the eye 

 from every part of the spectrum except that under observation. 

 The words in my book written at the time are, " narrow slit found 

 to be best at focus of little telescope with positive eyepiece." In 

 the note the second slit was stated to have been placed before 

 the object-glass of the little telescope. Such an arrangement was 

 tried in connexion with some other experiments in progress at 

 the time. The plan of limiting the field of view to the part of 

 the spectrum corresponding to the refrangibility of the light of 

 the prominence, as well as the employment of a ruby glass, is of 

 value when the air is not favourable, or when a spectroscope of 

 small dispersive power is used. 



Jan. 30.— G-eorge Busk, Esq., Vice-President, in the Chair, 



The following communication was read : — 



" On Just Intonation in Music ; with a description of a new 

 Instrument for the easy control of all Systems of Tuning other 

 than the ordinary equal Temperament of twelve divisions in the 

 Octave." By E. H. M. Bosanquet, Fellow of St. John's College, 

 Oxford. 



The object of this communication is to place the improved systems 

 of tuning within the reach of ordinary musicians ; for this pur- 

 pose the theory and practice are reduced to their simplest forms. 



A notation is described, adapted to use with ordinary written 

 music, by which the notes to be performed are clearly distin- 

 guished. 



The design of a key-board is described, by which any system of 

 tuning, except the ordinary equal temperament, can be controlled, 

 if only the fifths of the system be all equal. The design is 

 on a symmetrical principle ; so that all passages and combinations 

 of notes are performed with the same handling, in whatever key 

 they occur. 



The theory of the construction of scales is then developed; 

 and a diagram is given, from which the characteristics of any re- 

 quired system can be ascertained by inspection. 



An account is then given of the application of such systems 

 to the new key-board, and particularly of an harmonium which 

 has been constructed and contains at present the division of 

 the octave into fifty-three equal intervals in a complete form. 

 Rules for tuning are given. 



Finally, the application of the system of fifty-three to <the 

 violin is discussed. 



Throughout, the work of former labourers in the same field 

 is reviewed : the obligations of the writer are due to Helmholtz, 

 the late General T, Perronet Thompson, 'JBYR.S., and others. 



X2 



