The purpose of this book is to provide the reader with a series of work­ ed examples in X -ray spectrometry and X -ray diffractometry, in such a way that each example can be treated either as a posed question, i. e. one to which the reader must himself provide an answer, or as a guide to the method of treating a similar problem. The latter, of course, also provides a check on the answer produced by the reader. Although much basic theory can be derived by study of this work the first intention of the book is not to provide a source of basic theoretical knowledge in X -ray analysis. It is hoped that the book will be utilized more as a guide line in the tackling of theoretical and practical problems and as a means of estab­ lishing whether or not the reader is able to work out for himself a certain type of problem. For example, the series of examples on counting statis­ tics has been chosen in such a way that after working through and understanding these, the reader should be able to handle most of the calculations that he is likely to come up against in this area.