This is neither a technical manual, nor a treatise dealing with the history of a particular branch of applied science, but it partakes somewhat of the character of both. It is an attempt—perhaps somewhat bold—to present in a popular form an account of the great industry which has arisen out of the waste from the gas-works. In the strictest sense it is a romance of dirt. To render intelligible the various stages in the evolution of the industry, without assuming any knowledge of chemical science on the part of the general reader, has by no means been an easy task, and I have great misgivings as to the success of my effort. But there is so much misapprehension concerning the history and the mode of production of colouring-matters from coal-tar, that any attempt to strip the industry of its mystery in this, the land of its birth, cannot but find justification. Although the theme is a favourite one with popular lecturers, it is generally treated in a superficial way, leaving the audience only in possession of the bare fact that dyestuffs, &c., have by some means or other been obtained from coal-tar. I have endeavoured to go somewhat beyond this, and to give some notion of the scientific principles underlying the subject. If the reader can follow these pages, in which not a chemical formula appears, with the same interest and with the same desire to know more about the subject that was manifested by the audience at the London Institution, before whom the lecture was delivered, my object will have been accomplished. To the Board of Managers of that Institution my thanks are due for the opportunity which they have afforded me of attempting to extend that popular knowledge of applied science for which there is such a healthy craving in the public mind at the present time.

R. M.

6 Brunswick Square, W.C.