Mr. Griffin, gardener to Mrs. Wells, of Cowley, near Exeter, has published the following remarks upon this mode of circulating hot-water.

"The open trough, or gutter, may be applied to a boiler of any construction. The water flows from the top of the boiler, through a four-inch pipe, into troughs made of cast iron, of the following dimensions; inside measure six inches wide at the top, three inches and a half at the bottom, and seven inches deep; the trough is constructed in lengths three feet long, neatly fitted together by a rivet in the bottom, and one on each side near the top. The water returns in a cast-iron pipe, three inches in diameter. There are thin iron lids or covers, of the same length at each portion of the trough, to fit upon the whole length of the apparatus, so that the degree of humidity may be regulated by making up some portions of the covers, without disturbing the others. The troughs or gutters might be made of various materials, but I prefer iron. The heat is diffused from the surface of the trough or pipes, nearly as quickly as it would be from copper or zinc, and retains the heat much longer. The width and depth of the troughs should be varied according to the plants intended to be grown in the house. An orchidaceous house requires a wider surface on the top than those intended for the growth of erica; and green-house plants generally.

During the resting season of orchidaceous plants, the atmosphere of the house is easily kept less humid, by not removing the whole or any part of the lids.

"For vineries and peach-houses, it would answer exceedingly well, and entirely eradicate the red spider; for the trough can be covered when the trees are in (lower, and when the fruit is approaching towards maturity. On the other hand, during the growing season you may maintain a regularly humid atmosphere with less trouble than by any other means. In a pine-stove, forty feet long, with a walk between the back wall and bark bed, the trough being two feet from the level of the walk, Mr. Griffin says, ' I can command any degree of heat with much less attention than is required for some houses with a boiler of the same description, and equal power as regards pipe.' " - Gard. Chron.