Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. The author believes that the abundance and variety of his working material entitles him to consider his formulae and tables as universally applicable to the calculation of any dynamo. Although being intended as a text-book for students and a manual for practical dynamo-designers, anyone possessing a but fundamental knowledge of arithmetic and-algebra will by means of this work be able to successfully calculate and design any kind of a continuous-current dynamo, the matter being so arranged that all the required practical information is given wherever it is needed for a formula.