356 NOTICES OF THE MEETINGS [Jan. 27, 
WEEKLY EVENING MEETING, 
Friday, January 27. 
Cou. Pair J. Yorxz, F.R.S., Pres. Chem. Soc., in the Chair. 
Joun Tynvatt, Esq., Ph. D., F.R.S., 
Proressor oF NATURAL PHILOSOPHY, ROYAL INSTITUTION. 
On the Vibration and Tones produced by the Contact of Bodies having 
different Temperatures. 
In the year 1805, M. Schwartz, an inspector of one of the smelting 
works of Saxony, placed a cup-shaped mass of hot silver upon a cold 
anvil, and was surprised to find that musical tones proceeded from 
the mass. In the autumn of the same year, Professor Gilbert of 
Berlin visited the smelting works and repeated the experiment. He 
observed, that the sounds were accompanied by a quivering of the 
hot silver, and that when the vibrations ceased, the sound 
ceased also. Professor Gilbert merely stated the facts, and made no 
attempt to explain them. 
In the year 1829, Mr. Arthur Trevelyan, being engaged in 
spreading pitch with a hot plastering iron, and once observing that the 
iron was too hot for his purpose, he laid it slantingly against a block 
of lead which chanced to be at hand; a shrill note, which he com- 
pared to that of the chanter of the small Northumberland pipes, pro- 
ceeded from the mass, and, on nearer inspection, he observed that the 
heated iron was in a state of vibration. He was induced by Dr. 
Reid of Edinburgh to pursue the subject, and the results of his 
numerous experiments were subsequently printed in the Transactions 
of the Royal Society of Edinburgh. 
On the Ist of April, 1831, these singular sounds and vibrations 
formed the subject of a Friday Evening Lecture by Professor Faraday, 
at the Royal Institution. Professor Faraday expanded and further 
established the explanation of the sounds given by Mr. Trevelyan 
and Sir John Leslie. He referred them to the tapping of the hot 
mass against the cold one underneath it, the taps being in many cases 
sufficiently quick to produce a high musical note. The alternate ex- 
pansion and contraction of the cold mass at the points where the hot 
rocker descends upon it, he regarded as the sustaining power of the 
vibrations. The superiority of lead he ascribed to its great expansi- 
bility, combined with its feeble power of conduction, which latter 
prevented the heat from being quickly diffused through the mass. 
Professor J. D. Forbes of Edinburgh was present at this Lecture, 
