Rapidly he told as much as was necessary to convince the man that no further damage could possibly ensue, but he found the man hard to convince.
“But I declare,” Roger insisted, “the lycopodium and stuff that you saw blazing up through the skylight was just fireworks compounds, made up—I begin to think—for just that use. It made a grand glow, but probably blazed only in a tray. The room it was in is fireproof. Our film is all non-flam, in sealed or airtight cans. Our chemicals are in airtight containers.”
He added that his check of the tell-tale, on the brief entry he had made, disclosed no entrances by others. Such was impossible.
“Then how was the stuff ignited? Spontaneous combustion.”
“I suppose some gas was left open, on purpose, that would in time penetrate to the chemicals in the mixture. But the heat of that little couple of pounds of powder burning ten minutes would not raise our fire-thermostat more than a degree, and it must go up six or eight to set off the alarm.”
“The alarm came in, young fellow. How?”
Roger took him across to a drug store. In its window, against the wall, a huge advertising thermometer registered Fahrenheit degrees and stood at sixty-four. He hurried the man back, showed him the small interconnected thermometer for registering air temperature, against which the other inside one reacted. This one stood at fifty-five.
“Somebody wanted the alarm set off to lure me here—simple trick. Only had to hold ice on this one till it dropped eight degrees below the other and then the other would be eight above it and off went the alarm.”
Fire, an alarm adjusted for heat, set off by ice! Toby? Who else?