"But isn't a cyclone a low-pressure thingummy?"

"Yes."

"And didn't you say that B was a high-pressure place?"

"Yes."

"Then how does the air coming from B manage to be low-pressure stuff?"

"I see what you mean. There _is_ an explanation, but it would take too long
to hazard it now. Suppose the air is coming from B in an anti-cyclone, then
..."

"All right. I'll suppose that."

"... it rushes over to A and fills up the gap. There is more pressure at A
and the barometer goes up--"

"Is it fine then?"

"No, it rains. You see, the air from B is colder than the air at A was
before the air came from B."

"I _don't_ see."

"Well, obviously it _must_ be."

"How 'obviously'?"