Pouring some tap water into the cup, and filling it about one third full, he began to stir it round and round with a thermometer. The mercury in the tube quickly dropped, until it read 50°, showing the temperature of the water.
"Now, Ross," said Anton, "pour in the ice-water slowly."
Ross picked up the pitcher and began to let the water trickle in a tiny stream into the bright tin cup. Anton went on stirring.
Steadily the mercury descended in the tube as the water in the cup grew colder and colder. Ross poured in more and more slowly. Then suddenly, quite suddenly, while both boys were watching, the brightness of the tin cup clouded over, as though with a sudden fog. Anton drew out the thermometer and looked at it.
"The dew-point's only thirty-four," he cried, "and as we've got to figure frost at three or four degrees lower, it'll be so cold that there won't be any fog to stop a freeze. Ross, it's just the night for a killing frost. What do you think we'd better do?"
The older lad hesitated.
"If you don't mind, Anton," he said, "I'll stay to supper, and we'll see what your night observations say."
By evening the threats of a frost were even more definite and the two boys consulted what had best be done.
"I can easily get Father to start his fire-pots," said Ross, "we got them all fixed up this winter. Bob's dad has got some fruit, and we can warn him by wireless, and we could get a lot of the fellows together. I don't want to make a mistake, though. If we suggest that the fire-pots ought to be started and then it doesn't freeze, we'll hurt the League a lot more than we'll help it."
"I wish we could talk it over with Mr. Levin," said Anton, "but he's down with one of his sick spells and we oughtn't to disturb him. Whatever we do, we've got to do it on our own."