WILLIAM .sy/-:j//:.Y.v, I-.R.S. 89 



visual organ by the emanation of light, which again is neither 

 more nor less than vibratory motion imparted by the ignited 

 substance to the medium separating us from the same. According 

 to this theory, which constitutes one of the most important 

 advances in science of the present century, heat, light, electricity 

 and chemical action are only different manifestations of " energy 

 of matter," mutually convertible, but as indestructible as matter 

 itself. 



Forms of Energy. Energy exists in two forms, " dynamic " or 

 " kinetic energy" or force manifesting itself to our senses as weight 

 in motion, as sensible heat or as an active electrical current ; and 

 "potential energy" or force in a dormant condition. In illustration 

 of these two forms of energy, I will take the case of lifting a weight, 

 say one pound one foot high. In lifting this weight kinetic, mus- 

 cular energy has to be exercised in overcoming the force of gravita- 

 tion of the earth. The pound weight when supported at the higher 

 level to which it has been raised, represents " potential energy " to 

 the amount of one unit or " foot pound." This potential energy 

 may be utilised, in imparting motion to mechanism, during its 

 descent, whereby a unit amount of " Work " is accomplished. A 

 pound of carbon then, when raised through the space of one foot 

 from the earth, represents, mechanically speaking, a unit quantity 

 of energy, but the same pound of carbon when separated or, so to 

 speak, lifted away from oxygen, to which it has a very powerful 

 attraction, is capable of developing no less than 11,000,000 foot 

 pounds or unit quantities of energy whenever the bar to their 

 combination, namely, excessive depression of temperature, is re- 

 moved ; in other words, the mechanical energy set free in the 

 combustion of one pound of pure carbon is the same as would be 

 required to raise 11,000,000* pounds weight one foot high, or as 

 would sustain the work which we call a horse power during 

 5 hours 38 minutes. We thus arrive at once at the utmost limit 

 of work which we can ever hope to accomplish by the combustion 

 of one pound of carbonaceous matter, and we shall presently see 



* In burning 1 Ih. of carbon in the presence of free oxygen, carbonic acid is 

 produced and 14,500 units of heat (a unit of heat is 1 Ib. of water raised through 

 1" Fahr. ) are liberated. Each unit of heat is convertible (as proved by the de- 

 ductions of Mayer and the actual measurements of Joule)' into 774 units of force 

 or mechanical energy ; hence 1 Ib. of carbon represents really 14,500 x 774 = 

 11,223,000 units of potential energy. 



