"That's a good one, too, because high winds and steady rain seldom go together.
"The last type of clouds, which is Number Ten in the Weather Bureau Classification, is called Stratus. It really looks like a lifted fog, which sometimes it is. Indeed, there is no essential difference between clouds and fogs, anyway, except that fogs are formed at the surface and clouds above it."
"All clouds are fogs, sir?" said Anton, in a surprised voice.
"Yes, my boy. Clouds are visible water vapor. Their visibility depends largely on condensation, just as rain depends largely on the dew-point."
"What's the dew-point, sir?"
"The dew-point," the Forecaster explained, "is the temperature at which the air becomes so full of vapor that it can't hold any more without letting it down as rain or snow. It's never the same any two days in succession, because the air can hold more water vapor when it is warm than when it is cold."
"Is that why muggy days are so uncomfortable?" asked Ross.
"Yes. When the air is full of water vapor, it hasn't the same readiness to absorb it. When you perspire on a dry, hot, windy day, the air absorbs it right away, but on a day that's humid or muggy, the air can't hold any more, so it doesn't evaporate and the perspiration trickles down your back and into your eyes. A moist climate feels hotter in the summer and colder in the winter than a dry one, although, in reality, it isn't as hot or as cold. Every moist climate is a cloudy climate, and Ireland—which is called the Green or Emerald Isle because there's so much rain that none of the vegetation ever dries up—has some of the most beautiful clouds in the world."
"Is there any place in the United States without clouds?" asked Ralph.
"There's no place in the world that's absolutely cloudless," was the answer, "but clouds in some deserts are few and far between. There's one well known hotel, in the Southwest, that advertises 'free board every day that the sun doesn't shine.' It's a safe offer, too, for last year they only lost two days on it. There are some clouds there, but not such as to obscure the sun.