CHAPTER XVIII. PUZZLING QUESTIONS. It was not until the Projectile had passed a little beyond Tycho's immense concavity that Barbican and his friends had a good opportunity for observing the brilliant streaks sent so wonderfully flying in all directions from this celebrated mountain as a common centre. They examined them for some time with the closest attention. What could be the nature of this radiating aureola? By what geological phenomena could this blazing coma have been possibly produced? Such questions were the most natural things in the world for Barbican and his companions to propound to themselves, as indeed they