THE DISSIPATION OF ENERGY. 703 



simple straight line, their motion would be uniform and undifferenced ; 

 but, as neither the position nor the size of a mass undergoes change 

 when temperature does not vary, atomic paths must suffer oft-repeat- 

 ed stops. Elastic particles in this state must have incessantly fluc- 

 tuating velocities, yet always oscillating about a fixed mean. Mat- 

 ter endued with heat cannot have its particles in absolute contact, or 

 the compressibility or contractibility which is the inseparable property 

 of any mass would not exist. For argument's sake, however, let it 

 be admitted that from absolute contact or any other cause heat-mo- 

 tion is a uniform one. If it be a purely axial rotation, then the equa- 

 tors of the atoms move faster than the poles, and the movement is 

 not homogeneous. Exactly so, if the atom describe as an orbit a 

 circle, ellipse, or other figure recurrently. Such motion would in- 

 volve axial rotation, the atom would resemble our earth, and different 

 parts of it would move with different velocities. In the case of two 

 tangible spheres of like dimensions it is easy to show that, when swift- 

 ly moving at an equal rate, the speed of the one can be accelerated at 

 the expense of the other, by applying it at a point not equatorial to 

 the equator of its neighbor. In some such way it is conceivable that 

 differences in molecular motion may widen from those subsisting be- 

 tween the parts of an individual molecule. 



The imperfect homogeneity of thermal motion, which is here con- 

 tended for, has some palpable parallels in the distribution of two 

 other phases of energy electricity of high tension and magnetism ; 

 these forces are cumulative in their manifestations, increasing in 

 intensity toward the poles of the masses presenting them. 



Thirdly, it is not strictly an accurate premise in the theory that, 

 when heat is produced from any other force, it is unaccompanied by 

 any phase of energy not thermal. Increments of heat invariably alter 

 the dimensions of bodies, as a rule expand them, and thus part of the 

 original energy applied appears as gravity. The sun in warming the 

 earth's atmosphere lifts it, and, when the air cools, its fall is of no in- 

 significant dynamic value. What is so evident in this extreme case 

 is true of any mass whatever when heated. Not only is heat pitted 

 against gravity, but at times against cohesive and crystalline forces, 

 which, though overcome, must modify and diminish its effects. 



There is a check to the continuous increase of temperature which 

 is of much more importance than those just noted, but akin to them. 

 A compound substance receives additions of heat with tolerable even- 

 ness up to a certain point, when it is resolved into two or more sim- 

 ple constituents, according to its complexity. These if compound are 

 in turn decomposed into their chemical elements if more heat be ap- 

 plied. Now, chemical energy is a motion quite distinct by itself, and 

 we find that heat in its higher degrees must coexist with it. So that 

 on this account we cannot accept the notion that heat is ever to be- 

 come the only kind of motion in the universe. In so doing we recog- 



