Effect of Bodies on Light and Heat. 401 



pear to indicate that the higher the pitch of the radiant energy, the more 

 of it gets through. Experiments show that the same laws in regard 

 to the transmission of heat govern in liquids and vapors. The hotter 

 the source of the heat the more of it gets through. And, a liquid which 

 can be vaporized behaves in the same way in both states ; that is, it al- 

 lows the same relative proportion of the heat to pass through in the 

 liquid state that it does in the state of vapor. Water is a great absorber 

 of heat both as a liquid and a vapor. The difference in the transparency 

 of bodies to the waves of light and heat is due to the difference in their 

 molecules, or rather in the spaces between the molecules and between the 

 atoms which constitute the molecules. These spaces are occupied by 

 the ether and every space has a fundamental pitch due to its shape, the 

 same as a resonator has its fundamental for sound. If the ether waves 

 from a hot body upon reaching another body do not happen to have 

 periods corresponding to the fundamentals of the spaces in the body, 

 they wiggle on through, as a sound out of pitch passes through a resona- 

 tor without setting it in vibration. And these waves represent the 

 transmitted heat if they be long waves belonging to the lower end of the 

 44th octave and to the octaves below it, or the transmitted light if they 

 belong to the upper part of the 44th octave. The undulations that fail 

 to get through the body are those which vibrate in unison with the fun- 

 damentals in the body and expend themselves in starting and maintain- 

 ing by their continuous action, the internal vibrations in the body, which 

 show themselves in the increased heat of the body or in the work of 

 placing the molecules on a strain, as will be explained directly. This 

 heat not transmitted through the body is said to be absorbed. 



The mechanical nature of heat has been known for a hundred years. 

 It has long been understood to be the energy of the vibrating molecules 

 of a physical body, and the laws of its interconvertibility with other 

 forms of energy are well understood. Wherever it ceases as heat, it is 

 to be found as some other form of energy, either in action or potential. 

 What is called " latent heat, " it is now known, is energy expended in 

 producing a rearrangement of the molecules in the body into which it 

 has disappeared, and when this rearrangement is allowed to undo itself 

 the energy consumed in its production again appears as heat. Thus, 

 after ice has been raised in temperature to 32 F. , it will require 143 a 

 more of heat to raise its molecular structure from that of ice to that of 

 water, for after the 143 heat has been expended on it, it becomes water 

 with a temperature of 32. If now 180 more heat be expended on it, 

 its temperature will be 212 at which point the water boils. But still 

 it is water, and now 967 degrees more heat may be expended on it be- 

 fore it becomes steam, and at that moment its temperature is still just 

 212. So we know that the work of tearing apart the ice crystals in a 



