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SCIENCE. 



[N. S. Vol. II. No. 40. 



cent form, a very perfect hygienic light. 

 Where rivers are at hand the electrical 

 transnaission of power will drive railway 

 trains and factories economically, and 

 might enable each artisan to convert his 

 room into a workshop, and thus assist in 

 restoring to the laboring man some of the 

 individuality which the factory has tended 

 to destroy. In 1843 Joule described his 

 experiments for detei'mining the mechanical 

 equivalent of heat. But it was not until 

 the meeting at Oxford, in 1847, that he 

 full}' developed the law of the conservation 

 of energy, which, in conjunction with New- 

 ton's law of the conservation of momen- 

 tum, and Dalton's law of the conservation 

 of chemical elements, constitutes a com- 

 plete mechanical foundation for physical 

 science. 



Who, at the foundation of the Associa- 

 tion, would have believed some far-seeing 

 philosopher if he had foretold that the 

 spectroscop3 would analyze the constituents 

 of the sun and measure the motions of the 

 stars; that we should liquefy air and utilize 

 temperatures approaching to the absolute 

 zero for experimental research; that, like 

 the magician in the 'Arabian Nights,' we 

 should annihilate distance by means of the 

 electric telegraph and the telephone; that 

 we should illuminate our lai'gest buildings 

 instantaneously, with the clearness of day, 

 by means of the electric current; that by 

 the electric transmission of power we 

 should be able to utilize the Falls of Niagara 

 to work factories at distant places ; that we 

 should extract metals from the crust of the 

 earth by the same electrical agency to 

 which, in some cases, their deposition has 

 been attributed? 



These discoveries and their applications 

 have been brought to their present condi- 

 tion by the researches of a long line of 

 scientific explorers, such as Dalton, Joule, 

 Maxwell, Helmholtz, Herz, Kelvin and 

 Rayleigh, aided by vast strides made in me- 



chanical skill. But what will our succes- 

 sors be discussing sixty years hence ? How 

 little do we j^et know of the vibrations 

 which communicate light and heat! Far 

 as we have advanced in the application of 

 electricity to the iises of life, we know but 

 little even yet of its real nature. We are 

 only on the threshold of the knowledge of - 

 molecular action, or of the constitution of 

 the all-pervading ether. Newton, at the 

 end of the seventeenth century, in his pre- 

 face to the ' Principia,' says: "I have de- 

 duced the motions of the planets by mathe- 

 matical reasoning from forces; and I would 

 that we could derive the other phenomena 

 of nature from mechanical principles by the 

 same mode of reasoning. For many things 

 move me, so that I somewhat suspect that 

 all siieh may depend on certaru forces by 

 which the particles of bodies, through 

 causes not yet known, are either urged 

 towards each other according to regular 

 figures, or are repelled and recede from 

 each other; and these forces being un- 

 known, philosophers have hitherto made 

 their attempts on nature in vain." 



In 1848 Faraday remarked: " How rapid- 

 ly the knowledge of molecular forces grows 

 upon us, and how strikingly every investiga- 

 tion tends to develop more and more theii- 

 importance. A few years ago magnetism 

 was an occult force, aifecting only a few 

 bodies; now it is found to influence all bodies, 

 and to possess the most intimate relation 

 with electricity, heat, chemical action, light, 

 crystallization; and through it the forces 

 concerned in cohesion. We may feel en- 

 couraged to continuous labors, hoping to 

 bring it into a bond of union with gravity 

 itself" 



But it is onlj' within the last few years 

 that we have begun to realize that elec- 

 tricity is closely connected with the ^'ibra- 

 tions which cause heat and light, and 

 which seem to pervade all space — vibra- 

 tions which maj' be termed the voice of the 



