1870.] BARKER — ON VITAL AND PHYSICAL FORCES. 423 



is not as perfect. The best steam-engines economize only one- 

 twentieth of the heat of the fuel.'^ Hence if a steam ship require 

 GOO tons of coal to carry her across the Athmtic, 570 tons wiU be 

 expended in heating the waters of the ocean, the heat of the 

 remaining 30 tons only being converted into work. 



One other quantitative determination of force has also been 

 made. Prof. Julius Thomsen, of Copenhagen, has fixed experi- 

 mentally the mechanical eqaivaleat of light. '^ He finds that the 

 energy of the light of a spermaceti candle burning 126|- grains 

 per hour, is equal in mechanical value to 13-1 foot pounds per 

 minute. The same conclusion has been reached by Mr. Farmer, 

 of Boston, from difi"erent data.'* 



If we pass from the actual physical energies or motions to con- 

 sider for a moment the potential energies or attractions, we find, 

 also, an intimate correlation. Since all energy not active in motion 

 is potential in attraction, it follows that in the attractions we have 

 energy stored up for subsequent use. The sun is thus storing up 

 energy : every minute it raises 2,000,000,000, tons of water to the 

 mean height of the clouds, 3|- miles ; and the actual energy set free 

 when this water f^dls is equal to 2,757,000,000,000 horse 

 powers.*' So when the oxygen and the zinc of the ore are 

 separated in the furnace, the actual energy of heat becomes the 

 potential energy of chemical attraction, which again becomes 

 actual in the form of electricity when the zinc is dissolved in an 

 acid. We see, then, that not only may any form of force or 

 actual energy be stored up as any form of attraction or potential 

 energy, but that the latter, from whatsoever source derived, may 

 appear as heat, light, electricity, or mechanical motion. 



Having now established the fact of correlation for the physical 

 forces, we have next to inquire what are the evidences of the cor- 

 relation of the vital forces with them. But in the first place it 

 must be remarked that life is not a simple term like heat or elec- 

 tricity ; it is a complex term, and includes all those phenomena 

 which a living body exhibits. In this discussion, therefore, we 

 shall use the term vital force to express only the actual energy of 

 the body, however manifested. As to the attractions or the 

 potential energy of the organism, nothing is more fully settled in 

 science than the fact that these are precisely the same within the 

 body as without it. Every particle of matter within the body 

 obeys implicitly the laws of the chemical and physical attractions. 

 No overpowering or supernatural agency comes in to complicate 



