When the four of us decided to collaborate to write this book on pneumatic conveying, there were two aspects which were of some concern. Firstly, how could four people, who live on four different continents, write a book on a fairly complex subject with such wide lines of communications? Secondly, there was the problem that two of the authors are chemical engineers. It has been noted that the majority of chemical engineers who work in the field of pneumatic conveying research have spent most of their time considering flow in vertical pipes. As such, there was some concern that the book might be biased towards vertical pneumatic conveying and that the horizontal aspects (which are clearly the most difficult!) would be somewhat neglected. We hope that you, as the reader, are going to be satisfied with the fact that you have a truly international dissertation on pneumatic conveying and, also, that there is an even spread between the theoretical and practical aspects of pneumatic conveying technology.