48 



the price of Gommon bell-metal) and superioiity of tone. Other 

 alloys of iron, copper, zinc, manganese, and nickel were exhibited, 

 some bearing a near resemblance to gold, others to silver ; the 

 latter being now most extensively made in Birmingham, and gra- 

 dually superseding German silver, or at least being largely used in- 

 stead of that alloy, which it surpasses in lustre, closeness of texture, 

 and freedom from tarnish. A malleable bell was also shown, the 

 tone of which was equal, if not superior, to that of a common bell 

 of same size : a specimen of this sort of metal was shown crushed 

 almost flat. The author recommended its use for ship and light- 

 house bells, &c. 



3. On the Dynamical Theory of Heat, with Numerical Results 

 deduced from Mr Joule's Equivalent of a Thermal 

 Unit, and M. Regnault's Observations on Steam. By 

 William Thomson, M.A., Fellow of St Peter's College, 

 Cambridge, and Professor of Natural Philosophy in the 

 University of Glasgow. 



Sir Humphrey Davy, by his experiment of melting two pieces of 

 ice by rubbing them together, established the following proposition : — 



" The phenomena of repulsion are not dependent on a peculiar 

 elastic fluid for their existence, or caloric does not exist;" and he 

 concludes that heat consists of a motion excited among the particles 

 of bodies. " To distinguish this motion from others, and to sig- 

 nify the cause of our sensation of heat," and of the expansion or 

 expansive pressure produced in matter by heat " the name repulsive 

 motion has been adopted."* 



The Dynamical Theory of Heat, thus established by Sir Humphrey 

 Davy, is extended to radiant heat by the discovery of phenomena, 

 especially those of the polarization of radiant heat, which render it 

 excessively probable that heat propagated through vacant space, or 

 through diathermane substances, consists of waves of transverse 

 vibrations in an all-pervading medium. 



* From Davy's first work, entitled " An Essay on Heat, Light, and the Com- 

 binations of Light," published in 1799 in " Contributions to Physical and Me- 

 dical Knowledge, principally from the West of England ; collected by Thomas 

 Beddoes, M.D. ," and republished in Dr Davy's edition of his brother's collected 

 works, vol. ii. London, 1836. 



