The Writings of Benjamin Franklin. 1 59 



" May not all the phenomena of light be more con- 

 " veniently solved by supposing universal space filled with a 

 " subtle elastic fluid, which, when at rest, is not visible, but 

 " whose vibrations affect that fine sense in the eye, as those 

 " of air do the grosser organs of the ear ? We do not, in 

 " the case of sound, imagine that any sonorous particles are 

 " thrown off from a bell, for instance, and fly in straight 

 " lines to the ear ; why must we believe that luminous 

 " particles leave the sun and proceed to the eye ? Some 

 " diamonds if rubbed shine in the dark, without losing any 

 " of their matter. I can make an electric spark as big as 

 " the flame of a candle, much brighter, and therefore visible 

 " further ; yet this is without fuel ; and, I am persuaded, no 

 " part of the electric fluid flies off in such case, to distant 

 " places, but all goes directly, and is to be found in the 

 " place to which I destine it. May not different degrees of 

 " the vibration of the above-mentioned universal medium, 

 " occasion the appearance of different colours ? I think 

 " the electric fluid is always the same ; yet I find that 

 " weaker and stronger sparks differ in apparent colour, some 

 "white, blue, purple, red ; the strongest white; weak ones 

 " red. Thus different degrees of vibration given to the air, 

 " produce the seven different sounds in music, analogous to 

 " the seven colours, yet the medium, air, is the same. 



" If the sun is not wasted by expence of light, I can 

 " easily conceive that he shall otherwise always retain the 

 " same quantity of matter ; though we should suppose him 

 " made of sulphur constantly flaming. The action of fire 

 "only separates the particles of matter, it does not annihilate 

 " them. Water, by heat raised in vapour, returns to the 

 <' earth in rain ; and if we could collect all the particles of 

 " burning matter that go off in smoke, perhaps they might, 

 " with the ashes, weigh as much as the body before it was 

 " fired : And if we could put them into the same position 

 " with regard to each other, the mass would be the same as 

 "before, and might be burnt over again. The chymists 

 " have analised sulphur, and find it composed, in certain 



