Beside the invention of so many of the mechanisms now taken for granted, the makers of clocks (originally) and of watches (subsequently) invented the terms and phraseology to identify and describe them, originating, in the process, special toos with special names. thus it comes about that few crafts have such a wealth of words of special and, ofter, of unique significance. The horologist has his own names for his specialities and tools, sometime more than one for the same thing. And where tow or more are apt, or equally descriptive and equally well known, it is difficult to say which is right; which should be used and which ignored. So the writer of books on horology finds the choice of words before him more lavish than precise, a difficulty which was before me in writing Practical Watch Repairing. The inclusion of a glossary appeared a way to overcome it. But the glossary in itself became nearly as large as the book! So the only other way was to complete the glossary, deal with the definitions on encyclopedic lines and to do the job thoroughly with hundreds of illustrations and hang the expense! Fortunately this was also the publisher's opinion.