On the Pianoforte Bridges. 113 



and the energy necessary to overcome the molecular attraction 

 and cause the molecules to fly apart to an infinite distance is, 

 from equation 1, since D = 0, 



^^=^s/^c calories (25) 



.Equation 23 may therefore be written : 



p fi'^/dc _ energy necessary to overcome molecular attraction 

 2Et 2 X kinetic energy of molecules 



. . . (26) 



I give the values of Ek obtained from equation 21 and of 

 C as obtained from equation 26 in Table III. It' the values 

 of C there shown be compared with the average value of C 

 for the substance in question as given in Table II. a satisfactory 

 agreement will be noted. 



I have cited these relations because they indicate some 

 simple and deep-seated relation between the energy of mole- 

 cular attraction and the temperature energy. I do not pretend 

 to understand the significance of these relations clearly myself. 

 But of this I feel sure, the fact that it is possible to dis- 

 tinguish and find a simple relation between the energy of 

 molecular attraction and the kinetic (temperature) energy of 

 the molecules at the critical temperature points to the correct- 

 ness of the conclusion formerly reached, namely : Change of 

 temperature does not change the nature or the amount of the 

 molecular attractive force. The temperature merely determines 

 the orbit that the molecules loill follow in obedience to the 

 attractive force. 

 Camden, S. C, U.S.A., 

 Dec. 9th, 1910. 



VI. The Pianoforte Bridges. By G. H. Berry *. 



[Plate I.] 



IN every pianoforte there are two bridges : one of which 

 we may call the fixed bridge, which is the higher in 

 the Upright pianoforte and nearer the key-board in the 

 Grand ; and the other we may call the free bridge, which is 

 glued and screwed direct to the sound-board in both types 

 of instrument. 



The fixed bridge is usually of metal and forms part of the 

 framing of the pianoforte. It is practically rigid and not 

 directly connected to the sound-board, and therefore plays 



* Communicated by Prof. E. H. Barton, D.Sc, F.R.S.E. 

 Phil. Mag. S. 6. Vol. 22. No. 127. July 1911. I 



