This book does not pretend to teach inventors how to be their own attorneys, nor how to pre pare and prosecute an application for Patent. The time-worn adage that he who is his own lawyer has a fool for a client; is as true of patent law as it is of other branches. It would be impossible even within the scope of 'a much larger volume to go into the details of patent practice. An attorney or solicitor becomes skillful in the drawing and prosecution of patent cases not so much from any reading of text books as by constant application of the law every day to concrete examples. It is not so much. That he is learned in the fundamental principles which any one may learn for himself as that he is learned and experienced in the application of these princi ples. Each case differs in detail from every other and what at first sight seems-the most simple may turn out to be the most complex and subtle.