24 Prof. Forbes's Researches on the Vibrations which take place 



23. The next experiments were made with silver. Even 

 with very unfavourable apparatus it appeared remarkably ac- 

 tive as a vibrator. A small block of heated silver placed in a 

 hot vice, gave indications of being at the very top of the series 

 of vibrators, a cold lead bar being used ; a result fully con- 

 firmed 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 vibra- 

 tions are very sensible. 



27. From accidental circumstances, copper was one of the 

 last metals I tried ; when I had not the means of experiment- 

 ing accurately 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 intensity of vibration on lead, I had an indirect 

 way of confirming the results which will immediately be no- 

 ticed. The arrangement of metals in relation to their intensity 

 of vibration with lead, determined by a great series of experi- 

 ments, of which I have now given the principal results, be- 

 comes the following : 



Standard Silver (best). 



Copper. 



Standard Gold. 



Zinc. 



Brass (nearly the same as zinc). 



Platinum. 



Iron. 



Tin. 



Antimony; does not vibrate. 



Bismuth ; ditto. 



28. This arrangement indicates very distinctly the order in 

 which the metals possess the property or properties essential 

 to vibration with regard to lead. But a very important inquiry 



