Brick-built flues for hothouses

2112. The best sort of flues, after all that has been said on the subject, is, in our opinion, the common form, built of thin well-burned bricks neatly joined, with the bottom and top of tiles, and no plaster used either inside or outside. Where only one course of a flue can be admitted, the broader it is the more heat will be given out as it proceeds, and, as a consequence, one extremity of the space to be heated will be hotter than the other; a return or double course of a narrow flue is, therefore, almost always preferable to one course of a broad flue.