"Now the third one in the classification is very familiar. That's the well-known mackerel sky. What's the rhyme about that, Dan'l?"
Proud at being thus appealed to, the darky quoted triumphantly:
"Mackerel scales and mares' tails,
Make lofty ships carry low sails."
"That's correct," said the weather expert, "because those clouds foretell wind. Sometimes the cloud flakes are less solid and look like the foam in the wake of a steamer.
"Beneath them come the alto clouds, which are made up of drops of moisture instead of crystals of ice. The fourth class, called alto-stratus, is a thick sheet of gray or bluish color, sometimes thin enough to let the sun shine through. When lower and in heavy roundish masses it's called alto-cumulus, which is the fifth on the list, and when it is lower still and looks like a lot of great blue-gray footballs wedged closely together it is known as strato-cumulus."
He shuffled the prints rapidly, selecting types of clouds as he did so, and pencilling on the back the character of the cloud.
"Then comes the cumulus, the big round cloud, that looks like masses of fluffy cotton wool piled on top of each other. These are the 'woolpack clouds,' which, in summer time, throw deep shadows on the grass. It is this cloud which, when it comes between you and the sun, gives rise to the old saying that 'every cloud has its silver lining.'"
"Those aren't the thunder clouds, sir, are they?" the photographer asked.
"No," the Forecaster answered. "The thunderstorm clouds are called cumulo-nimbus. They're heavy masses of cloud rising in the forms of mountains or towers. Isn't there a rhyme about clouds and towers, Dan'l?"
"Yas, suh, there's a rhyme," the old darky replied, and he quoted: