ically active than powdered quartz, yet it will bleach oil as thoroughly as is possible in any way.

Some valuable suggestions concerning the composition of shop and field coats are given at the end of Chapter XLI in the data supplied by Messrs. Chalfant and Covell.

There seems to exist among engineers a notion that it is unprofessional for a technical writer to recommend in print any special make of paint. Such a tenet, however, is fundamentally wrong, as is also the idea that one should not call for any particular material of any kind in his specifications. If an engineer is confident that a certain material will suit his proposed construction better than any other, he should have the courage of his conviction and should call for its use, even if he has to run the risk of evil-minded persons insinuating that he was illegitimately influenced so to do. Similarly, when a technical writer has learned from long experience that certain materials are best for certain purposes, he should be sufficiently brave and independent to give to his brother engineers the benefit of his accrued knowledge.

For many years the author has favored red lead for the shop coat, provided that it were honestly manufactured, honestly mixed, honestly applied, and honestly dried before being either covered or subjected to possible abrasion. Again, experience has taught him that the pigment should not be delivered at the shops as a powder or even as a paste, but that the paint should be previously mixed and ready for use; because the caliber of the men employed for shop-painting is generally so small that they cannot be trusted properly to mix the paint, hence it has usually occurred that the mixture was lumpy, that thinners were illegitimately added, and that the coating was daubed on the steel irregularly, being too thick in some places and too attenuated in others.

Year after year the author has continued his search for an ideal shop coat; and it was not until a short time ago that he found it in Dutch Boy Red Lead. At first he could obtain this only in either powder or paste form, with which it was impracticable to obtain perfect results; but finally he persuaded the manufacturers to furnish it ready mixed, using to one American gallon of pure raw linseed oil twenty-eight pounds of the pigment thoroughly incorporated by grinding with the oil. He is now satisfied that he has discovered what he has been searching for during more than three decades. For the field coat he has had the most satisfactory results with Goheen's Carbonizing Coating, Nobrac, and Detroit Graphite, although at one time long ago, as will be explained further on, the latter paint failed him.

Other engineers have had good luck with other finishing coats—for instance, those recommended by Cheesman & Elliot, Lowe Brothers' "Metalcote," and Toch Brothers' "Tockolith." Lowe Brothers' "Red Lead Lute" has given good satisfaction as a shop coat; and for that purpose many users pin their faith on Cheesman & Elliot's No. 31 Red Oxide. A