172 ANNUAL OF SCIENTIFIC DISCOVERY. 



and we in consequence find here what has been determined in steam- 

 engines, in which the useful work done is more nearly expressed by the 

 heat lost in the fall of temperature, in proportion as the machines are more 

 perfect. 



M. Regnault shows clearly how much his new experiments are opposed 

 to the old hypothesis, which made caloric a fluid, at one time in the latent 

 state, at another disengaged and sensible ; he shows, on the other hand, 

 how easily they are explained on the theory which attributes heat to a 

 vibratory motion ; the principle of the preservation of moving forces then 

 suffices to account for all the transformation of heat into work, and vice 

 versa. After insisting upon the fact, that the theory by which Laplace 

 corrected Newton's formula for the velocity of the propagation of sound in 

 air, and explained the considerable differences between the calculated and 

 observed velocities, is no longer admissible, he expresses an ardent desire 

 to see some new series of experiments on the velocity of sound in air, 

 water and solid bodies, taking advantage of all the recent progress of sci- 

 ence and the mechanic arts. 



ON THE VIBRATION AND TONES PRODUCED BY THE CONTACT OF 

 BODIES HAVING DIFFERENT TEMPERATURES. 



The following is an abstract of a paper read before the E, oyal Institution 

 by Prof. Tyndall, F. K S. :- 



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 engnged 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 compared to that of the chanter of the 

 small Northumberland pipes, proceeded from the mass, and, on nearer 

 inspection, he observed that the heated iron was in a state of vibration. 



Professor Faraday, after giving the subject some attention, 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 expansion 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 

 expansibility, combined with its feeble power of conduction, which latter 

 prevented the heat from being quickly diffused through the mass. 



Professor Forbes, of Edinburgh, then took up the subject, and rejects 



