The daily morning journal and courier., 1895-06-21
COURIER FRIDAY, JUNE 2 l895


 versed in all directions by myrlads of waves.
 The profoundest mathematical ye- searches applied to the most refined experiments have so far only confirmed
 that theory in every particular.
 Having learned what light is we must now inquire how light is pro- duoed. All matter is composed of very small particles called molecules Be- tween these molecules are spaces called pores. When you heat any body It's molecules are thrown into vibration.
 They move to and fro, come into col- lision, bound and rebound The faster these molecules move the hotter the body becomes. Heat then is nothing but the motion of the molecules of a body.
 Now when any body is sufficiently heated it gives out light, That is its molecules when moving with great ra- pidity strike with such force against the surrounding ether that light waves are produced When the molecules of body vibrate with such rapidity that light is produced the body Is said 10 be incandescent. All the artificial sources of light ever devised by man depend upon the development of light during incandescence.
 Whether the light be obtained from candles gas, oil or electricity, or what ever the source, in every case some body must be heated to incandescence.
 In order that light may be bright in nearly all cases it is necessary to heat some solid to incandescence for a | OVllx .l feeble Illuminating power.
 This fact may be easily demonstrated by experiment.
 T have large flame of burning coal gas the same as we use for illumina- ting our dwellings. It gives considera- ble light.
 This light is due to the incandescence of particles of solid carbon which is one of the constituents of coal gas, I hold this clean white plate in the flame You see it is covered with black soot.
 This is the solid carbon. The bright ness of the light is due to the incandes- cence of the solid particles.
 When the coal gas burns it's copstit- uents combine with the oxygen of the air and pass off as gaseous products. If there is not a sufficient supply of air to consume all the ingredients of the gas at once the carbon particles float for time unconsumed and their incan- descence produces the light 1 To show that this is the case I will pump into the flame large supply of air.
 | The carbon is immediately consumed. The brightness of the light disappears. We will give another experimental proof of the same fact.
 Here is an almost Invisible flame made by burning oxygen and hydro- gen.
 To prove that the flame is intensely hot place in 1t this iron wire. It is 1 immediately consumed. I will now in- sert a stick of lime. The lime does not burn, but Is soon heated to incandes- cence and a very intense light is given out. will now ask you to consider the method by which light is obtained from electricity in our systems of electric lighting We will take 1t for granted that all are aware that there is such an agent as electricity; that 1t can be ob- tained from a battery, dynamo or in other ways; that it will flow through a wire or other conductor from its source clear around the circuit back to it's starting point, and finally that the di- rection of the flow of the current in the wire may be reversed at will.
 One important fact, however, of which We must make use I will now de- monstrate. If wire through which an electric current Is flowing is held over a compass or magnetic needle the nee dle is defected or turned to one side.
 have here a large magnetic needle fixed for convenience in vertical posi- ton. Now if join the ends of these wires which lead to the dynamo in the electric power house on George street a l current will flow through the entire circuit. A portion of the wire is passed around the magnetic needle, the index of which now stands at zero.
 We will now close the circuit, the l current flows and we see the needle is | defiected. The deflection of magnetic | needle thus indicates that an electric | current is passing If the Reflection is large the current is evidently strong, if | small it is weak
 With these preliminary observations l we may now consider how electric en- ergy is converted into light. Experi- ments show that if the electric current | be passed through long wire or fine wire or some substance which is natu- rally a poor conductor the current is weakened Through this large copper wire I pass the current we see the de- flection is ten degrees Since the wire | which conveys the electric current is large 1t offers no great resistance and so the current is strong. Upon this frame are wound several turns of rath- CT fine wire. I place this wire in the circuit the Reflection is only five de- grees. This shows that a fine wire re- sists the current and weakens it. But why" you ask, "is the current weak ened in passing through the long small wire? What becomes of the electric energy?" If you place your hand near these coils of wire your question will be answered. We find that the wire has become hot. We thus learn that when a electric current is resisted by con- ductor the current weakens, but the heat in the conductor increases. Elee- tric energy is thus through resistance into heat. If now, as we have already shown, we continue to heat the wire hotter and hotter until it's molecules move so rapidly as to throw