the Formation of Organic Bodies. 225 



lies, on the contrary, occasion a tendency to decomposition, a 

 species, in short, of fermentation, in which, of consequence, there 

 is a separation of oxygen, and water remains behind. But what is 

 peculiarly interesting is, that the same effect is produced not only 

 by the action of such bodies as are soluble in this liquid, but also 

 of various solid bodies, some organised and others unorganised ; 

 as, for example, by the peroxide of manganese, silver, platina, 

 gold, and even by the fibrine of blood. The substance whicli 

 produces the decomposition undergoes no alteration ; nor does 

 it become an element of the new compound, and therefore it 

 operates by an inherent power, which, though unknown as to 

 its essence, is, nevertheless, demonstrated by its effects. 



Shortly before this discovery of M. Thenard, Sir H. Davy 

 had noticed a phenomenon, the connection of which with the 

 preceding was not immediately recognised. He had proved 

 that platinum, heated to a certain extent, and brought into con- 

 tact with a mixture of the vapour of alcohol, or of ether, and 

 atmospheric air, possessed the power of producing the combina- 

 tion of these bodies, whilst other substances, such as gold and. 

 silver, had not this property. 



A short time after this, Mr E. Davy found that a prepara- 

 tion of platinum in a state of extreme mechanical division had 

 the power, at ordinary temperatures, and after being mois- 

 tened with alcohol, of becoming incandescent by the combustion 

 of alcohol, at the same time changing this liquid by oxidation 

 into acetic acid. 



After this followed the discovery of Dobereiner, which was 

 the most important of them all. He demonstrated the property 

 which spongy platinum has of setting fire spontaneously to a 

 current of hydrogen gas projected into atmospheric air ; a phe- 

 nomenon which the researches of Thenard and Dulong extend- 

 ed to many other bodies, both simple and compound, but with 

 this restriction, that, whilst platinum, iridium, and some other 

 metals of similar character, acted at temperatures below 32°Fahr., 

 those other bodies, such as gold, and still more silver, required 

 much higher temperatures, and glass a heat of 300° or more. 



Thus, this property, which at first was considered as acting 

 in a way that was altogether singular, appeared to be a general 

 property, though acting differently in relation to different bo- 



