The aim of the Author in writing this treatise has been to produce a text-book useful to students attending technological classes, so that they may be enabled to supplement their knowledge gained in the class-room, and thus assist the instructor to cover a larger field than is possible under ordinary circumstances. It will also serve, it is hoped, as a handbook to some instructors by suggesting matter for teaching and demonstration in their classes.

To those unable to avail themselves of the advantages offered by the various classes held throughout the country, the work will be interesting and instructive.

It is to be noted that the book has not been prepared for use as a "cram" book, and care has been taken to treat the various subjects to minimize any such tendency.

The Author's best thanks are due to those who have lent blocks, etc., for use in this and the second volume.