116 SCIENCE Itf SHORT CHAPTERS. 



though written so long ago, appears to ine worthy of the 

 profoundest present consideration. 



" It appears to me that heat and light may be considered as 

 affections ; or, according to the undulatory theory, vibrations 

 of matter itself, and not of a distinct ethereal fluid permeating 

 it : these vibrations would be propagated just as sound is 

 propagated by vibrations of wood or as waves by water. To 

 my mind all the consequences of the undulatory theory flow as 

 easily from this as from the hypothesis of a specific ether ; to 

 suppose which namely, to suppose a fluid sui generis and of 

 extreme tenuity penetrating solid bodies we must assume, first, 

 the existence of the fluid itself ; secondly, that bodies are 

 without exception porous ; thirdly, that these pores communi- 

 cate ; fourthly, that matter is limited in expansibility. None 

 of these difficulties apply to the modification of this theory 

 which I venture to propose : and no other difficulty applies to 

 it which does not equally apply to the received hypothesis.'* 



CHAPTER XVII. 



ON THE SOCIAL BENEFITS OF PARAFFINS. 



To the inhabitants of Jupiter, who have always one, two, or 

 three of their four moons in active and efficient radiation, or 

 of Saturn displaying the broad luminous oceans of his mighty 

 rings in addition to the minor lamps of his eight ever-changeful 

 satellites, the relative merits of rushlights, candles, lamps, and 

 gaslights may be a question of indifference ; but to us, the 

 residents of a planet which has but one small moon that only 

 displays her nearly full face during a few nights of each month, 

 the subject of artificial light is only second in importance to 

 those of food and artificial heat, and every step that is made 

 in the improvement of our supplies of this primary necessary 

 must have a momentous influence on the physical comfort, and 

 also upon the intellectual and moral progress, of this world's 

 human inhabitants. 



If a cockney Rip Van Winkle were to revisit his old haunts, 

 the changes produced by the introduction of gas would probably 

 surprise him the most of all he would see. He would be 



