Improvements in Science. 223 



inversely as the square of the distance. Molecules consist 

 of a collection of atoms kept at a distance by attractive and 

 repulsive forces peculiar to each atom. Atoms are material 

 points from which these attractive and repulsive forces 

 emanate. 



From this definition, it follows, he considers that a mole- 

 cule is essentially solid, whether the body to which it belongs 

 be solid, liquid, or gaseous; that the molecules are poly- 

 hedrons, of which these atoms, or at least a certain number 

 of these atoms occupy the summits, and it is these polyhe- 

 drons that are termed primitive forms by crj r stallographers. 

 The particles alone can be separated by mechanical means. 

 The force which results from the vibrations of the atoms 

 may separate the compound into simpler molecules. Che- 

 mical action can alone separate the latter. Thus, in deton- 

 nating a mixture of 1 volume of oxygen and 2 volumes of 

 hydrogen, by which 2 vols, of vapour of water are formed, 

 each molecule of oxygen is divided into two, and the atoms 

 of each of these halves unite with the atoms of a molecule 

 of hydrogen to form a molecule of water. Proceeding upon 

 these premises, Ampere distinguishes the vibrations of 

 molecules from those of atoms. In the first, the molecules 

 vibrate together, approaching and retreating alternately 

 the one from the other, and whether they vibrate in this 

 manner or remain at rest, the atoms of each molecule vi- 

 brate, and in fact, always do vibrate by approaching and 

 retreating the one from the other alternately, without 

 ceasing to belong to the same molecule. The latter, he 

 terms atomic vibrations. To the vibration of the molecules, 

 and to their propagation in the surrounding media he attri- 

 butes all the phenomena of sound ; to the vibrations of the 

 atoms he ascribes all those of heat and light.* 



3. Optical properties of Charcoal. — If a portion of well 

 burned fir charcoal be placed upon a layer of heated coal 

 on a wind furnace, and all openings be closed, so that no 

 air can penetrate below the coal, the combustion will be 

 carried on entirely by the decomposition of the carbonic 

 acid. After the fire has subsided, Degen found that the 

 portion of coal had wholly or in part dissolved into a mass 

 of fibres, which did not adhere strongly to each other. 

 * Ann. de Chim. «'t de I'bys. lviii. 



