136 Radiant Forces. 



PLEASANT WAYS IN SCIENCE. 



No. V. — Eadiant Forces. 



If a candle is placed in the centre of a room, it diffuses light 

 equally in all directions, and consequently all parts are lit in 

 regular proportion ; upwards, downwards, on this side, and on 

 that go the light rays, and if an obstacle meets them, they 

 pass on either side of it, leaving a shadow behind it. The 

 candle flame gives light because it is full of incandescent par- 

 ticles, each of which behaves in the manner mentioned ; and 

 we may figure the minutest conceivable particle bristling all 

 round with light rays, which we might roughly imitate by 

 sticking pins as close together as possible all round a tiny cork 

 ball. We might approximate a little nearer to the truth, but 

 yet be almost infinitely far from the wonderful minuteness of 

 nature, by drawing with the finest pencil an immense number 

 of the most delicate lines as close together as possible, and all 

 radiating from one point, which would represent an incan- 

 descent particle distributing its light rays in one plane only, 

 whereas the real particle distributes them in all planes.* 



It is easy to draw two lines on a sheet of paper, diverging 

 from the same point so gradually and so close together at the 

 commencement, that at a distance of two or three feet they 

 should be a very little way apart. Suppose, however, we were 

 required to draw two such lines, which) commencing a slight 

 divergence in London, should be found only an inch apart at 

 York, how impossible would be the task. Still more impossible 

 would it be for us to draw two lines for a few feet or a few 

 inches which should have only such a rate of divergence that 

 they would nearly touch each other if prolonged round the 

 globe to New Zealand, or were extended some 240,000 miles 

 off, until they reached the surface of the moon. The sun is 

 about 92,000,000 of miles from the earth, and yet, according 

 to the explanations usually given, each incandescent par- 

 ticle of his photosphere sends forth rays so tightly packed 

 together, that many pairs of them reach our earth without 

 the distance between them having become perceptible, not- 

 withstanding they have been getting further apart from 

 each other every yard they have advanced in their enormous 

 journey ! Still more astounding is it to conceive that the sun 

 sends to the remote planet Neptune, which is more than thirty 

 times as far from that luminary as our earth is, sets of 

 diverging rays so closely packed/ that many pairs of them 



* An orange may be eut through its centre into slices, each slice representing 

 one of tl e innumerable planes into which it may be conceived capable of division. 



