176 Molecules, Ultimates, Atoms, nnd Waves, [April, 



some cases adds to their number, but it does not affect the 

 breadth of the individual lines. Where it adds to their 

 number, the new lines are always developed towards the 

 violet end of the spectrum. They correspond to quicker 

 rates of vibration, the same order being followed as in the 

 case of incandescent solids and liquids. A diminution of 

 pressure narrows and weakens the lines, sometimes ex- 

 tinguishing them altogether. An increase of pressure 

 brightens or blackens the lines, and adds considerably to 

 their breadth. When the increase of pressure becomes very 

 great, the breadth of the bright lines becomes so augmented 

 that they ultimately blend and form a continuous spectrum, 

 as if the substance had become liquid or solid, although it 

 nevertheless continues in the gaseous condition. This last 

 phenomenon indicates a development of adventitious inertia, 

 in virtue of which the atoms that, under a more moderate 

 pressure, vibrated at only certain definite rates, are, under the 

 influence of the augmented pressure, compelled to vibrate at 

 various rates, and behave like the particles of solid and liquid 

 bodies. The most obvious explanation of this fact is, that the 

 chemical ultimates are really very complex in their structure. 

 While they consist of atoms having different degrees of in- 

 trinsic inertia, in virtue of which they tend, when freed from 

 all adventitious inertia, to vibrate at only certain specific rates, 

 nevertheless even the lightest ultimates consist of a con- 

 siderable number of such atoms ; so that, when they are 

 forced into greater mutual proximity by strong pressure, 

 they act and react on each other by their atomic attractions 

 in such a manner as to develop within the limits of the 

 ultimate an inertia of position, in virtue of which the con- 

 stituent atoms vibrate at a much greater variety of rates. 



