Mr Russell on the Vibration of 



Fig. 4. 



A 



Fig. 5. Fig. 6. 



7' 



Fig. 7. 



A 



Fig. 8. 



390 



the middle ; and in like 

 manner simultaneous oscil- 

 lations were propagated 

 through the whole struc- 

 ture with a continually in- 

 creasing amount, until they 

 at last injured it. 



The method of cure 

 which I adopted, was sim- 

 ply to alter the place of the 

 cross bars at m, bringing 

 them down, as shewn at m\ 

 Fig. 5, and this simple 

 change was attended with 

 remarkable results, inas- 

 much as the vibration was 

 ■very greatly reduced, even 

 though a larger portion of 

 the upper division was thus left to the action of the wind with- 

 out transverse support. 



I next proceeded to make experiments upon the effect of 

 altering the place of the support m. I placed it as in Fig. 6, at 

 m"\ one-third of the length from the bottom, and there were 

 now vibrations as at first of great violence, only with a less 

 range and with greater velocity, and it is most worthy of re- 

 mark, that the point .r, which was not fixed by any support, 

 nevertheless remained stationary in the same manner as if it 

 had been fixed. 



The support being next placed at m"'\ as in Fig. 7, being one- 

 fourth part of the whole length of the beam from the bottom, 

 the oscillations took place, as shewn in the figure, in four divi- 

 sions, the points z/ and ti- at equal distances apart remaining 

 stationary. The oscillations were less extensive and more rapid 

 than formerly, but still of great force and duration. 



Finally, it was ascertained that, by placing m the support at 

 such a point, that its distance from the fixed points A and B 

 bore to each other no simple proportion of length, the propa- 

 gation and increase of oscillations are entirely prevented. Fig. 8. 



Philosophical Explanation, — It is easy to account for these 



