560 THE POPULAR SCIENCE MONTHLY. 



The same means will serve in storing solar heat, and, if need he, ship- 

 ping it to a distance. We have harely outlined the idea, hut certain 

 we are that at the proper time the scientific man will appear who shall 

 discover a practical method of doing this. 



The sun, as it would appear, will be the fuel of the future, and one 

 might say that this was foreseen by the great encyclopaedic scholar 

 of the middle ages, Dante, when in his incomparable poem he said, 

 " Guarda il calor del sol che si fa vino " " Look at the sun's heat 

 which changes into wine" as though he meant to say, into all that 

 is force, all that is life, all that is light. Revue des Deux Mondes. 







THE KEYIVED THEORY OF PHLOGISTON. 



Br WILLIAM ODLING, M. B., F. K. S. 



FULLEKIAN PROFESSOR OF CHEMISTRY, ROYAL INSTITUTION. 



IN 1781 '83, Cavendish showed that when inflammable air or hydro- 

 gen, and dephlogisticated air or oxygen, are exploded together 

 in certain proportions, " almost the whole of the inflammable and 

 dephlogisticated air is converted into pure water," or, as he elsewhere 

 expresses it, "is turned into water." 



On June 24, 1783, the experiment of Cavendish was repeated on a 

 larger scale and in a somewhat different form by Lavoisier, who not 

 only confirmed the synthesis of the English chemist, but drew from it 

 the conclusion at first strongly contested, then rapidly acknowledged, 

 and since never called into question "that water consists of inflam- 

 mable air united to dephlogisticated air," or that it is a compound of 

 hydrogen and oxygen. 



This conclusion, so opposite to his own preconception on the 

 matter, Lavoisier subsequently confirmed by an analysis of water. 

 He found that iron, heated to redness and exposed to the action of 

 water-vapor, became changed, by an abstraction of oxygen from the 

 water, into the self-same oxide of iron procurable by burning the metal 

 in oxygen gas the other constituent of the water, namely, its hydro- 

 gen, being freely liberated. 



With the demonstration by Lavoisier of the composition of water 

 began the triumph of that antiphlogistic theory which he had con- 

 ceived, in a necessarily imperfect form, so far back as 1772, or before 

 the discovery of oxygen, and had brought to completion by the aid of 

 every successive step in pneumatic chemistry, achieved by himself or 

 by others. 



In 1785, the relationship to one another of hydrogen and water 

 being then conclusively established, Berthollet declared himself a con- 

 vert to the new theory of combustion put forward by his countryman. 



