48 DAVY. 



travel in France, whither he proceeded, accompanied by his lady 

 and Mr. Faraday. From France, Davy proceeded to Italy, where 

 he spent the winter, returning to London on the 23rd of April, 1814. 

 During his stay in Italy, he collected specimens of the colours used 

 by the ancients in their pictures. This formed the subject of a 

 memoir to the Royal Society, the most interesting part of the paper 

 being the announcement that the fine blues of the ancients were 

 formed of silex, soda, and copper, and that they may be exactly 

 imitated by strongly heating together, for the space of two hours, 

 three parts of copper filings, fifteen of carbonate of soda, and twenty 

 of powdered flint. 



In the year 1816, Davy turned his attention to a method of pre- 

 venting the dreadful accidents in coal mines, from explosions of the 

 fire-damp. After considerable investigation, he found that this gas 

 would not explode when mixed with less than six times or more 

 than fourteen times its volume of atmospheric air; and in the 

 course of experiments made for the purpose of ascertaining how the 

 inflammation takes place, he was surprised to observe that flames 

 will not pass through tubes of a certain length or smallness of bore. 

 He then found that if the length was diminished, and the bore also 

 reduced, that flames still would not pass ; and further, that the 

 length of the tubes might safely be diminished to hardly anything, 

 provided their bore was proportionably lessened. Working from 

 these principles, he proposed several kinds of lamps, but all were 

 finally superseded by the simple one known as the Davy safety- 

 lamp, in which a small oil light is covered by a cylinder of wire 

 gauze, the small apertures* of which flame will not pass through, 

 and the explosion is thus prevented from extending outside the 

 wire gauze. The introduction of this beautiful invention, although 

 freely given to the public, was for a time violently opposed by 

 prejudice and passion. Experience, however, showed the com- 

 parative safety which the miners who used it possessed, and the 

 coal-owners of Newcastle and the vicinity presented Davy with a 

 superb service of plate, as some recognition of the important benefit 

 he had conferred on them. 



During the later years of Sir Humphry Davy's life, various com- 

 munications appeared from him to the Royal Society, none, however, 

 presenting any very remarkable features. In November, 1820, a 

 few months after the death of Sir Joseph Banks, he was elected 

 president of the above society. In 1823 he repeated the interesting 

 experiment of Mr. Faraday, as to the condensation of gases by 

 mechanical pressure, and succeeded in converting sulphurous acid 

 and prussic acid gases into liquids, by heating them in" strong sealed 

 tubes. During the same year he investigated the causes of the 

 rapid decay of copper sheathing on ships, and attributing this to 



* The meshes or apertures of the wire gauze ought not to he more than one 

 twenty-second of an inch in diameter. Brougham's Lives of Philosophers. 



