.MEASURING THE VIBRATORY PERIODS OF TUNING-FORKS. 49 



following results. Tlio boats were timed with tlie aid of a stoi)-\vat(;li registering to oi)e-teiith of 

 a second. After each observation the (h)or was closed and lilteen niiiiiites alloweil to elajjse before 

 bej^inniiig the observations on the two forks ne.\t in order. I should here remark, however, that 

 tlie order in which tlie forks were experimented with was tlie reverse of that given in the table, 

 that is to say, the experiments began with the f/?':, fork, of highest pitch; because the smaller 

 mass of the higher forks would be most attecte<l by any change of temperature from interchange 

 of air of the rooms. I, however, observed no change in tlie tem])erature of the rooms ilnriiig the 

 experiments. 



Table II. 



Tlio two IT: folks gave 11. (j beats iu 60 seconils for a difference of 25° Falir. 

 The two VT^ forks gave '-j;t.O beats in 60 seeoiuls for a difference of ih'^ Fahr. 

 Tlie two SOLz forks gave '26.0 beats in 60 seconds for a dift'ereuce of 25° Fahr. 

 The two Ul\ forks gave 'i'i.h beats in 60 seconds for a difference of 25° Fahr. 

 The two Mli forks gave 67.6 beats in 60 seconds for a difference of 25° Fahr. 

 The two VTi forlvs gave 81.5 beats iu 60 seconds for a difference of 2.5° Fahr. 



The forks in the cold room were a set recently received of KcENia; those in tlie warm room 

 were a set of his forks which had been in constant use for several years and had become worn and 

 somewhat rusted. To ascertain the difference in the numbers of vibrations of cou'esponding forks 

 of the two sets, when at the same temperature, 1 had kept them for a day in the room which had 

 the teminratnre of 06° Fahr., and after they had remained at this temperature during four hours 

 we simultaneously sounded the two corresponding forks of tiie two sets with the following results: 



Table III. 



New rr,. fork g.ive 2..3 beats in 60 seconds, with old VT. fork. Old f.nk Mat. 



Kew CTj fork gave 5.0 beats iu 60 seconds, with old {/'J'n fork. Old fork flat. 



New SOL^ fork gave 2.0 beats in 60 seconds, with old .vOii fork. Old fork sliar)). 



New [Tj fork gave no beats in 60 seconds, with old [?T, fork. Old fork in unison. 



New JZ/i fork gave 12.0 beats in 60 seconds, with old MU fork. Old fork tlat. 



New J7Ts fork gave 12.0 beats iu 60 seconds, with old UT:, fork. Old fork flat. 



Coireeting the ob.servations of the number of beats given in Table II by the determination of 

 beats contained in Table III, we have tlie actual numbers of beats iier minute given V)y the forks 

 for a difference in temperature of 25° Fahr., if the fork had been strictly in unison when tit the 

 same temperature, as follows: 



Table IY. 



The two VT2 forks g.ave 9.:i beats in 00 seconds for a dill'eieuce of 25- Fahr. 

 The two fTj forks gave 18.0 beats in 60 secouds for a dift'ereuce of 25° Fahr. 

 The two .SOL;, forks gave 28.0 beats iu 60 secouds for a <liti'ereiice of 25° Fahr. 

 The two UTi forks gave 34.5 beats in 60 seconds for a difference of 25° Fahr. 

 The two illi forks gave 45.6 beats in 60 seconds for a difference of 25° Fahr. 

 The two J'T:, forks gave 6'.t.6 beats in 60 seconds for a difference of 2.5° Fahr. 



I'rom the above determinations it follows: 



Table V. 



— , -|-, 1" Fahr. gives JJTi fork -\-, — , .00600 of a vibration per secovd. 

 — , +, 1° Fahr. gives X'l\ fork -i-, — , .01200 of a vibration per secoud. 

 — , -|-, 1° Fahr. gives SOL^ fork +, — , .018660 of a vibration per secoml. 

 — , +, 1° Fahr. gives VT^ fork +, — , .023000 of a vibration per second. 

 — , -|-, 1° Fahr. gives Mh fork +, — , .0:)0400 of a viliration per second. 

 — , -I-, 1° Fahr. gives IT:, fork +, — , .0463:i:J of a viliration per .second. 



S. Mis. fiO 7 



