The Captain, as the oldest man in the party, claimed the privilege of saying he could stand it no longer. Striking a light, he consulted the thermometer and cried out: "Seventeen degrees below zero, centigrade! that is certainly low enough to make an old fellow like me feel rather chilly!" "Just one degree and a half above zero, Fahrenheit!" observed Barbican; "I really had no idea that it was so cold." His teeth actually chattered so much that he could hardly articulate; still he, as well as the others, disliked to entrench on their short supply of gas. "One feature of our journey that I particularly admire," said Ardan, trying to laugh with freezing lips, "is that we can't complain of monotony. At one time we are frying with the heat and blinded with the light, like Indians caught on a burning prairie; at another, we are freezing in the pitchy darkness of a hyperborean winter, like Sir John Franklin's merry men in the Bay of Boothia. _Madame La Nature_, you don't forget your devotees; on the contrary, you overwhelm us with your attentions!" "Our external temperature may be reckoned at how much?" asked the Captain, making a desperate effort to keep up the conversation. "The temperature outside our Projectile must be precisely the same as that of interstellar space in general," answered Barbican. "Is not this precisely the moment then," interposed Ardan, quickly, "for making an experiment which we could never have made as long as we were in the sunshine?" "That's so!" exclaimed Barbican; "now or never! I'm glad you thought of it, Ardan. We are just now in the position to find out the temperature of space by actual experiment, and so see whose calculations are right, Fourier's or Pouillet's." "Let's see," asked Ardan, "who was Fourier, and who was Pouillet?" "Baron Fourier, of the French Academy, wrote a famous treatise on _Heat_, which I remember reading twenty years ago in Penington's book store," promptly responded the Captain; "Pouillet was an eminent professor of Physics at the Sorbonne, where he died, last year, I think." "Thank you, Captain," said Ardan; "the cold does not injure your memory, though it is decidedly on the advance. See how thick the ice is already on the window panes! Let it only keep on and we shall soon have our breaths falling around us in flakes of snow." "Let us prepare a thermometer," said Barbican, who had already set himself to work in a business-like manner.