Scientific Lectures. 133 



brilliant combustion. "We can produce an intense degree of heat bj 

 oxygen and hydrogen combined, and a solid body placed in the flame 

 will glow with a certain degree of intensity. This is accomplished 

 in the ordinary way by the use of lime or by the employment of 

 magnesia, mica, platinum, or any substance that can be made 

 incandescent ; and thus we may get one of the most brilliant lights 

 of the present day. Here we have some compressed magnesia, and 

 here are four little jets of oxygen and carbureted hydrogen, and you 

 see that they produce a brilliant light. This is the form of light 

 with which you are familiar under the name of the Drummond 

 light, although the name which properly belongs to it is the Hare 

 light, for it was Prof. Hare, of Philadelphia, who first showed that 

 by the union of the two gases, oxygen and hydrogen in exactly the 

 proportions found in water, two v^olumes of hydrogen and one of 

 oxj^gen, we may produce this intense degree of light. You now see 

 [returning to the brick thoroughly heated in the flame] that the iron 

 becomes warm — the iron boils, the iron burns — and it gives us this 

 generous illumination. If we were to catch the little particles which 

 shower in every direction, they are particles of oxide of iron which 

 are thus produced ; and by increasing the force of the jets of gas we 

 might increase this shower of sparks until it rose to the ceiling. 

 This teaches us that we arc not only to consider intensity of light, 

 but also the volume of the liglit wliich we are to produce. You see 

 here the triumph of the discoveries of Sir Humphrey Davy, who 

 said that the crust of the earth was a mass of oxydized metals, that 

 at one time glowed with fervent heat ; that it was then a sun in 

 glory, although now a world higher in dignity than if merely an 

 empty sphere emitting a fierce light associated with chemical heat. 

 "We have here two compressed gases, as before, oxygen in the one and 

 carbureted hydrogen in the other receiver. You perceive that as we 

 allow the two to be discharged in jets of burning gas, we have very 

 little light ; but placing a pencil of compressed magnesia in the 

 flame, it produces a light pleasing to behold, and one of the modern 

 triumphs of science. In the one case we have heat, and in the other 

 light. It is by the adroit arrangement of these burners that we 

 produce this effect ; and it requires a nice adjustment of the two 

 gases to evolve the most intense light. 



Let me now ask you to observe what takes place when we employ 

 a simple candle flame. We have first the particles of hydrogen that 

 burn and form water : and then we have the minute atoms of carbon 



