The Edge Chronicles: Stormchaser (the 2nd book)

This book is by Paul Stewart & Crhis Riddell. In this book there is a powerful substance called stormphorax and there are people all over in the land of The Edge, who would do anything to get thier hands on some.there is a great iron ring to which a long and heavy chain extends up into the sky. At its end is an immense floating rock with a city built on it called Sanctaphrax. one man named Vilnix Pompolnius, became the most high academe of Sanctaprax by "inventing" phrax dust. He would steal some of the stormphorax (that kept Sactaphrax in place)from the treasury and grind it up into a powder to form phrax dust.he found out that by putting just one particle of phrax dust into the most filthiest water would make the water pure again. But the more he takes, the more that Sanctaphrax is on a verge of flying of into the open sky when the chain breaks. Finally the professor of light calls upon the most respected sky pirate named Quintinius Virginix (Cloud Wolf) to find more stormphrorax. He goes on his adventure leaving his son (Twig) behind (or so he thought) after they just reunited. but Twig becomes the hero and saves Sanctaphrax, but the journey is not over yet. His trusty friend the caterbird comes to tell him that his father is trapped in a great mind storm. So Twig gets a new sky ship of his own called the Edgedancer, and he also gets his own crew. He then sets of to find his father with the great caterbird leading the way.