Dr. A. Naumann on the Velocity of Atomic Motion. 375 



position of equilibrium increases, according to equation (1), in 

 proportion to the square root of the absolute temperature ; and 

 the amplitude of vibration increases at the same time. (It may 

 be remarked here, in passing, that it is evident from these consi- 

 derations that every compound body must be capable of being 

 decomposed by heat ; for as the vis viva of the atomic motion 

 continues to increase, and therefore also the amplitude of the 

 vibrations of the atoms, the attracting forces will, after a certain 

 limit, no longer be able to holdback the atoms within the sphere 

 of the molecule.) The velocity of the two atoms after they have 

 passed their position of equilibrium, moving towards each other, 

 will be quickly but continuously diminished down to zero in con- 

 sequence of the constantly increasing preponderance of the re- 

 pulsion; the atoms then begin to move back, and under the 

 influence of the repulsion, which acts as an accelerating force 

 until they come to their position of equilibrium, they arrive there 

 with their original velocity but moving in the opposite direction. 

 This velocity now rapidly diminishes down to zero, as they recede, 

 further from each other, in consequence of the greater and greater 

 preponderance acquired by the attraction; and then the opposite 

 movement takes place in obedience to the same forces. When 

 they reach the position of equilibrium, the atoms have again 

 acquired their original velocity, to the square of which (the body 

 being supposed always the same) the quantity of heat which pre- 

 sents itself in the form of atomic motion is proportional. 



The conditions of the movement of the atoms are less simple 

 when, as is for the most part the case, the molecule is composed 

 of several dissimilar atoms. But since in these more complex 

 cases also the total vis viva of atomic motion is proportional to the 

 number of atoms, we must assume that the vis viva of the sepa- 

 rate atoms is at least on the whole the same. The velocity cor- 

 responding to the thermal content, which expresses itself in the 

 motion of an atom, is the velocity which the atom would have if 

 the various attracting and repelling forces which act upon it mu- 

 tually held each other in equilibrium ; this is likewise the velo- 

 city which must be denoted as the intensity of vibration. Thus 

 if v' and v" represent these velocities for two atoms, and N' and 

 N" their masses, we have 



iNV 2 =iN'y' 2 , whence v"=v'\ /®L. 



2 - 3 V N" 



But, according to equation (1), we have for hydrogen, whose 

 specific gravity =p = 0*0692, 



0-8165 . 485 m \/ 274 ' 6 + ^ 

 V 274-6 . 0-06 



274-6 . 0-0692 



