LOSS OF HEAT AND LIGHT IN THE SOLAR SYSTEM. 515 



If the heat of the solar Bystem be motion, undulation, or vibration, and 

 is continually being diminished, it may be assumed to be but transitory, 

 and must have had a beginning, as there will be a time when it will entirely 

 cease in its near relation to our solar system. There must, too, have been 

 a cause adequate to give rise to the motion, undulation, vibration, or heat. 

 Now, what force could give rise to the vast volume of heat eontained in 

 the whole mass of matter of the solar system, while suspended in incan- 

 descent vapor, but the ultimate force of the entire mass of matter itself 

 drawn in and hurled together by its own unresisted attraction ? Any less 

 power would be inadequate to its production. That motion may be con- 

 verted into heat, and heat into motion, we see continually and familiarly 

 illustrated. Take a piece of wire between your thumb and finger, bend it 

 rapidly back and forth, and heat too great for the hand to endure will soon 

 be produced. Strike rapidlj-, wich a hammer, on a bar of iron — heat is the 

 result. Take a bar of steel with a blunt end, apply the end to a rapidly- 

 revolving emery-wheel, take hold of the middle of the bar with one hand, 

 and with the other grasp the opposite end — the hand in the center will ex- 

 perience no heat, while the end grasped by the other hand will soon be- 

 come so hot that the hand cannot endure it. This is caused by the obstruc- 

 tion offered by the hand to the lieat waves, set in motion by the emery- 

 wheel. A thermometer placed at the end of the bar will not indicate a 

 greater degree of heat, because it offers no resistance to the heat waves. A 

 ball discharged from a cannon, coming in contact with a stationary solid 

 body, or with another body moving rapidly in an opposite direction, be- 

 comes greatly heated, as, also, would the body in motion coming in contact 

 with it. Now, the heat so generated, after its cause has ceased, itself ceases, 

 being gradually dissipated, and the heated substance becomes cold. The 

 dispersion is in proportion to the mass of the body heated and the amount 

 of resistance offered to the vibration or heat waves. A small body will 

 lose its heat sooner than a large one, other conditions being equal. 



Heat, then, may have its origin in motion or arrested motion, and when 

 so originated is not permanent, but passes gradually away. The laro-est- 

 sized cannon-ball, heated to redness, soon loses its heat and becomes cold, 

 when the cause of its heat ceases. 



Suppose twQ cold balls or globes a mile in diameter, comj)osed of all the 

 elements of which the solar system is made up, moving in opposite direc- 

 tions, could be thrown together, each moving with a velocity of a hundred 

 miles per second, the heat imparted to them by the arrested motion — which 

 would be in proportion to the velocity with which they came in contact — 

 would be sufficient to drive off the matter of which i\\Qj were composed in 

 an incandescent gaseous condition. If they were removed beyond the in- 

 fluence of any attraction greater than their own, they would expand in 

 consequence of the heat generated by the impact, until the expansive force 

 of the heat was overcome by the central attractive force of the mass. 

 When the catastrophe which generated the heat was over, the dispersion 



