524 



Mr. A. J. Ellis. 



[June 17, 



efficients, deduced originally from a fork of 64 vibrations and extended 

 to one of 256. 



For 1° C. and 1 vib. For 1° F. and 1 vib. 



1st or general coefficient . . . 1-4-89*43 -00006212=1-4-16,097 



2nd or particular „ ... 1-4-8951 -00006207=1-4-16,112 



Tkese are practically the same, but it is the latter which he uses in 

 his reductions. Professor McLeod by his machine ("Proceedings," 1879, 

 vol. xxviii, p. 291, and " Phil. Trans.," 1880, p. 1) at first obtained a 

 result nearly identical with Koenig's, but afterwards, when experiment- 

 ing on one of my forks of about 440 vibrations, he found (private letter) 

 the coefficient to be '00004882 = 1-4-20,490. While Professor Alfred 

 Mayer (private letter) by repeated experiments on Koenig's and other 

 forks, exposed to the cold of American nights, and counted by beats 

 with forks at mean temperature, obtained the coefficient '00004545 = 

 1-4-22,000, and I adopted 1-4-21,000 as a mean of those of Professor 

 McLeod and Professor Mayer. The error must certainly be very 

 small for all Scheibler's forks. 



For organ pipes where great exactness does not seem to be possible, 

 I find the coefficient "00104 for 1° P. and 1 vibration quite sufficiently 

 accurate and to give concordant results generally. In some organs 

 where the air for blowing is cooler than the air of the room, this is too 

 large, according to the observations of Mr. A. J. Hipkins, at St. James' 

 Hall, the coefficient is nearer *0005 (private letter). In taking the 

 pitch of organ pipes by measured forks, I usually neglect the small 

 alterations of the pitch of the fork, and allow fully for the change of 

 pitch in the pipe. It is probable that this coefficient does not answer 

 for the stopped and fancy pipes. I have applied it only to open, and 

 generally metal cylindrical pipes. 



To construct the fork tonometer, invented by J. Heinrich Scheibler 

 (b. 1777, d. 1837), a silk manufacturer at Crefeld, obtain a set of about 

 70 good forks with parallel prongs, -and of a tolerably large size ; tune 

 the lowest to about the C (or B for English high pitch) between the bass 

 and treble staves of any organ or piano, and tune the rest roughly each 

 about four beats in a second sharper than the preceding. Then fit them 

 with wooden collars or handles, and allow them to rest for three months, 

 if possible in the same temperature at which they will be counted. 

 This was not the process adopted by Scheibler, but is much simpler. 

 Then count the beats between each set most carefully, at a temperature 

 which remains as uniform as possible. It may be necessary to use a 

 high temperature; thus Scheibler's was from 15° R. to 18° R. = 65'75 

 to 72 0, 5 P., which I reckon at 69° P. as a mean ; and Koenig now works 

 at 20° C. = 68° P., but announces that his former 256 vibrations was 

 only correct at 26°-2 C. = 79°-16P. ("Wied. Ann.," 1880, p. 413.) Count 

 on one day the beats between forks 1 and 2, 3 and 4, &c, and on 



