440 Prof. FORBES on the Vibrations which take place 



vibrators, a cold lead bar being used ; a result fully confirmed by 

 subsequent experiments, in which the temperature of 212 was 

 carefully ensured. 



24. My first observations upon gold led me to the conclu- 

 sion, that it is much inferior to silver in the scale of vibrators. 

 Subsequent experiments led me to place it third in the scale. 

 Standard gold was employed. 



25. Zinc vibrates with great facility and certainty upon lead, 

 when it has a temperature of 212; when hotter, it is subject to 

 some irregularities. Zinc and brass, to which it is closely allied, 

 seem to stand next to gold, being very superior to platinum and 

 iron, but considerably inferior to silver. 



26. Iron is very nearly allied to platinum, but, from very 

 careful experiments, is, we have seen, to be placed somewhat 

 lower. Tin stands decidedly below iron, and stands in the scale 

 next to lead, the cold metal employed, yet still its vibrations are 

 very sensible. 



27- From accidental circumstances, copper was one of the last 

 metals I tried ; when I had not the means of experimenting ac- 

 curately upon silver, I had no hesitation in placing copper at 

 the very top of the scale, so steady, forcible, and sustained were 

 its vibrations. I finally placed it below silver, but the difference 

 is not great. Besides the direct mode of observing the inten- 

 sity of vibration on lead, I had an indirect way of confirming the 

 results which will immediately be noticed. The arrangement 

 of metals in relation to their intensity of vibration with lead, de- 

 termined by a great series of experiments, of which I have now 

 given the principal results, becomes the following : 



Standard Silver (best.) 



Copper. 



Standard Gold. 



Zinc. 



Brass (nearly the same as Zinc.) 



