What a gay picture he is painting now, with his light-pencils; for in them, remember, and not in the things themselves the colour lies.

See how, where the hay has been already carried, he floods all the slopes with yellow light, making them stand out sharp against the black shadows of the wood; while where the grass is standing still, he makes the sheets of sorrel-flower blush rosy red, or dapples the field with white oxeyes.
But is not the sorrel itself red, and the oxeyes white?
What colour are they at night, when the sun is gone?
Dark.
That is, no colour.

The very grass is not green at night.
Oh, but it is if you look at it with a lantern.
No, no.

It is the light of the lantern, which happens to be strong enough to make the leaves look green, though it is not strong enough to make a geranium look red.
Not red?
No; the geranium flowers by a lantern look black, while the leaves look green.

If you don't believe me, we will try.
But why is that?
Why, I cannot tell: and how, you had best ask Professor Tyndall, if you ever have the honour of meeting him.
But now--hark to the mowing-machine, humming like a giant night-jar.