Sir Humphry Davy 115 



His connexion with the Royal Institution was finally 

 severed in 1813, and during the late autumn of that year he 

 set out accompanied by his wife and Faraday on what 

 he called a " journey of scientific enquiry." He was received 

 with great honour in Paris, where he attended the meetings 

 of the Academy of Science, which elected him a corre- 

 sponding member. On November 29th a paper was read 

 to the Academy on a new and remarkable substance dis- 

 covered by Courtois, which, when heated, gave out a violet- 

 coloured vapour. This was followed a week later by a 

 communication from Gay Lussac, pointing out its analogies 

 to chlorine and bromine, and proposing the name " iode " 

 for it. It is characteristic of the impetuous manner in which 

 Davy rushed through a research that, having obtained a 

 small quantity of the substance, he at once set to work, and 

 on December 20 a letter, in which he described his experi- 

 ments, was submitted to the Academy by Cuvier. After a 

 few days he forwarded his complete results to the Royal 

 Society, proposing the name of iodine as the English 

 equivalent for the new substance. 1 



Another example of Davy's activity during this journey 

 remains to be mentioned. At Florence he made use of the 

 great burning-glass belonging to the Accademia del Cimento, 

 by means of which it had already been shown in the reign 

 of Cosimo III. that a diamond is inflammable when the 

 rays of the sun are concentrated upon it. On repeating 

 the experiment Davy found that the products of combustion 

 consisted almost entirely of carbonic acid, and pronounced 

 diamond to be pure carbon. This result had an importance 

 greater than that which attaches to the record of a new 

 experimental fact; for it was the first well-established 

 instance of a chemical element existing in two different 

 now called allotropic forms. 



Shortly after Davy's return to England in 1815, a Society 

 that had been formed to discover, if possible, some method 

 by which explosions of fire-damp could be prevented, asked 



1 The French Academy began to publish its " Comptes Rendus " 

 only in 1835. For a reprint of the papers connected with the dis- 

 covery of iodine, the reader is referred to four communications in the 

 Annales de Chimie," vol. 87, pp. 304-329. 



H 2 



