PREFACE,The author trusts that this little handbook will fill a gap in the literature associated with the subject of Heating and Ventilation, though it will be recognised that the treatment of these two all-important subjects is not the direct purport of the present work. For, in the aspects of supplying heat in the one case, and of renewing the supply of air in the other, there is, indeed, no lack of books, but a work specifically dealing with the conduits for conveyance of the products of combustion from the grate to the external air seems to have long awaited production. And even now, far from any claim being advanced, that this book has the quality of exhaustiveness, it must be emphasised that it is to be regarded in no other light than as being an introduction only to the subject of ilue treatment. Its main value should prove to lie in the selective process pursued as regards what scientists and practical exponents have had to say on the subject. and this being so, it is the authors privilege and leasure to record the names of those who have permitted him to make selections from their writings, and also of those who assisted him in other directions. To the Institution of Structural Engineers where the author devoted four years as Secretary in the days of its currency as the Concrete Institute thanks are due for the interest shewn, and for placing him in touch with the Associated Portland Cement manufacturers for useful information in regard to factory chimneys, which was readily furnished, and this firm also approached Messrs. Tileman Co., whose co-operation in regard to practical information respecting the design of Reinforced Concrete tall chimneys has been to the benefit of this book, as perusal of later pages will make evident. Messrs. Tilemans kindness in lending blocks must also be acknowledged. Others to whom thanks are due are mentioned in the pages of the text. But special attention must be given here to the kindness of Messrs. J. Lyons Co., who lent a drawing of a brick factory chimney, from which the present author was permitted to prepare the Frontispiece, and it is only in accordance with the wishes expressed that the effective glazed brick lettering on the shaft was omitted from the drawing.