( 137 ) 



Notice regarding some Experiments on the Vibration of Heated 

 Metals. By ARTHUR TREVELYAN. 



(Read Ytth January and %lst March 1831.) 



IN the month of February 1829, I discovered accidentally that 

 a bar of iron, when heated and placed with one end on a solid 

 block of lead, in cooling vibrated considerably, and produced 

 sounds similar to those of an ^Eolian harp. 



1. I have lately made further experiments with bars of cop- 

 per, zinc, brass, and bell-metal, which, when heated and placed 

 on blocks of lead, tin, or pewter, produce the same effect as the 

 iron. 



2. The bars I generally used in making the experiments, 

 were 4 inches long, 1^ inch wide, and 1^ inch thick, with a rod 

 7 inches long attached to one end, to serve as a handle. A ridge 

 is formed along the centre of one side of the broad part, by its 

 being bevelled off towards each edge ; the other side is flat. The 

 longitudinal ridge is the part that rests on the block. 



3. A notch in the lead block, or a groove made along the ridge 

 which runs up the centre of the bar on the part where it rests 

 on the block, increases the sounds. 



4. The notes on two bars that I have tried, of different sizes, 

 at different temperatures, are in the key of E major, with four 

 sharps, commencing frequently with B natural in the bass. 



5. If the vibrating bar be placed on a piano-forte, and certain 

 notes be struck on the instrument, the vibration of the bar, and 



