“Well, in cubic feet, my dear—” commenced Sir John.
“No! no! Uncle John! I don’t understand cubic feet. Tell me how long our water would last.”
“With the utmost care we can carry enough water to last six people two months.”
“As long as that?”
“Yes, and then, should any unforeseen circumstances arise, by which we were unable to renew our water supply, I could fall back on a wonderful discovery I have made. See, my dear.” and he opened a small press. There, on shelves, were packed row upon row of transparent blocks, perhaps an inch square.
“What ever is it?” said Mavis, laughing. “Why, it’s camphor!” Alan picked a piece up and examined it. It was certainly like camphor to look at, but was odourless and of an intense coldness. “It’s done me. What is it?”
Sir John made no reply but took from a little stand a small electric heater. Upon this he placed a quart metal bowl, into which he put the little cube. “Very gentle heat at first, my dears,” said he. “Ah!” as it began to melt. “Now I think it’s safe to put on full pressure.”
Fascinated, they watched until the vessel became full of a sparkling, bubbling liquid. Turning on another electric switch, he plunged a metal needle into the fluid. It belched forth a cloud of steam, hissed violently and then calmed down.
“What ever is it?” asked Mavis. For answer, Sir John poured the liquid into three glasses and handed one to each.
“Try it,” he suggested. “It’s quite cold. That was an electric needle which generates a coldness below freezing point.”