Your directions to W. H. L. on this subject, in June number, are scarcely explicit enough to enable a person without experience to build a good furnace and flue, and having had something to do with flues I will, with your permission, supplement your article with a few additional directions, which shall at least have the merit of being practical.

If convenient, W. H. L. should make a cellar or pit adjoining the end of his greenhouse, and five or six feet in depth. The furnace should be built within the greenhouse, but the door should be open into the cellar, so as to exclude the dust and smoke from the plants. The cellar may be made large enough to answer for a coal house.

Furnace fronts and fixtures, consisting of a heavy casting, with two doors, metal grate-bars, etc, should be used; and the ash-pit of the furnace may be raised about a foot from the floor of the cellar.

The foundation and walls of the furnace should be strongly built, not less than eight inches in thickness; and all that portion exposed to the fire, as well as the first ten feet of the flue, should be built of the best fire-brick.

The size of the furnace will depend on the size of the house to be heated, and the fuel to be used. If the latter is to be wood mainly, the furnace should be larger than if coal or coke is to be burned.

For a greenhouse of fifty feet in length, where coal or coke is to be the fuel, a good size to make the furnace will be three feet long, eighteen inches wide and twenty inches high, above the bars. The arch for the top of the furnace may be built on a core of soil, rammed firm and trimmed to the shape desired.

The flue should rise from the back of the fur-nace to the level of the greenhouse floor, with a steep slope, and be built from thence to the foot of the chimney with a gradual rise. The steeper;his rise is the better the draught will be; but care must be taken not to interfere with doors and benches.

The instructions for building flues, usually met with, were evidently written by persons who lave used anthracite coal, or coke - as they speak of carrying them one hundred and fifty feet, with two or three bends, and but little rise, and no mention is made of any method of cleaning the flue.

In many parts of the country the fuel must necessarily be bituminous coal; and unless some provision is made to remove the soot and ashes from the flue, the destruction of the plants by gas will inevitably occur.

If the flue is built straight, with a uniform rise, and a door is made in the base of the chimney, opposite the entrance to the flue, the soot may be brushed into the furnace by a close-fitting swab.

The flue should be raised from the ground sufficiently to keep it dry, and should be built of good size, not less than eight inches wide and twelve inches high inside.

The bricks forming the side may be set on edge, but are* better when laid flat, and the top may be covered with narrow tile. The whole should be laid with good thin mortar, and the joints should be thoroughly plastered.

Build the chimney not less than twelve feet high, and let it rise six feet above any object near it.

Such a furnace and flue, if well built and kept clean, should do good service; but if W. H. L. intends to make floriculture a business, he will never be satisfied until he procures an efficient hot-water apparatus.

I began with flues, and many a cold night I have slept beside them, with no bed but a board, waking as the heat began to decline to replenish my fires.

My next step was to a simple form of boiler, but I made a mistake common to young florists who are struggling along with little means. I bought a boiler too small for its work, and that winter my wife and baby occupied a sleeping-room with me, improvised in the potting-shed, directly over my little heater, and every twc hours I wakened to fire up.

The next summer I put in a large boiler of the best construction, capable of heating twice the amount of glass I had in use. This I could leave without attention for twelve hours at a time, and I consider it the best investment I ever made.