122 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



required in order to separate these plates through a given 

 distance was inversely proportional to the force that was ap- 

 plied. It increased nearly as the inverse square of the original 

 distance between the plates, and as the fourth power of the 

 radius of the plates; and in whatever liquid he immersed his 

 plates, the times were proportional to those required by equal 

 volumes of these liquids to flow through capillary tubes. 

 19 <7,VIIL, CO. 



THE DISSIPATION OF ENERGY. 



In some remarks on the dissipation of energy, Lord Ray- 

 leigh states that the chemical bearings of this subject are 

 very important. A chemical transformation is impossible if 

 its occurrence involves the opposite of dissipation ; but it is 

 not true that a transformation which involves dissipation 

 must necessarily take place ; otherwise the existence of ex- 

 plosives, like gunpowder, would be impossible. The possi- 

 bility of chemical action must often depend upon the density 

 of the reacting substances. Thus, in the case of a mixture 

 of oxygen and hydrogen in proper proportions at a certain 

 density, the mixture may be exploded by an electric spark, 

 and energy be dissipated ; but beyond a certain point of 

 rarity the explosion can not be made, as it could not then 

 involve any dissipation. It may probably be found that 

 many mixtures which show no tendency to explode under 

 ordinary conditions, will become explosive when sufficiently 

 condensed. 



THE TRANSMISSION OF MECHANICAL POWER BY MEANS OF 



ELECTRICITY. 



Magneto -electric machines have not yet attained that 

 point of perfection which permits them to be placed among 

 the industrial apparatus; but they at least offer a method 

 of producing electricity very economically. The principal 

 machines are those of Siemens and Halske, of the French 

 Society of L' Alliance, and of Gramme. The currents pro- 

 duced in the last-named machines are analogous to those 

 furnished by the galvanic battery, thus permitting its ap- 

 plication to all works where voltaic electricity is useful. 

 The Gramme, as adapted for electro-plating in the silver- 

 works of Christoffle, of Paris, has a height of four feet and a 



