This is a subject of considerable interest to florists and greenhousemen. I have had a life experience with all kinds of heaters - from a forty-horse power, high pressure, steam boiler, down to a one dog power, common greenhouse flue, whose gassy emanations in cloudy weather would kill a toadstool at forty yards. For growing plants and flowers I would always give the preference to steam heating; but the great difficulty with high-pressure boilers is that they require constant attention, are not economical as to fuel and consume a great deal of water. This is overcome by the low pressure, self-regulating steam boilers.

I have an eight-section boiler, which heats about one thousand four hundred feet of one-and-a-fourth inch piping, purchased from and put up by, the Exeter Machine Works, of Exeter, N. H.

The boiler is below all the returns, so that all the water condensed in the pipes returns again into the sections. This water is heated when it comes back into the boiler, so that the process of steam making is not impeded, but goes steadily on. Forty-eight gallons of water fill my boiler and two gallons of water are wasted in a week. Each section is shaped somewhat like an oyster-can placed on its side, with holes on each end for two short pieces of pipe, which connect the sections with two oblong drums (upper and lower) outside the brickwork. On these drums are placed the paraphernalia of all steam boilers, with the addition of the weights and chains which adjust the drafts; and when the indicator reaches the point adjusted by the weights, it closes up all the drafts. The draft for fire can be adjusted by lengthening or shortening the chains to suit the weather. If such a thing as an accident should occur to any of the sections, it can be taken out and the drums plugged, and run without it until another section is procured.

Another feature is that additional sections can be put on, without in-terfering with the original sections.

My boiler will run six hours without attention, and the amount of hard coal burned (by computation) is about the same as that burned in common flues to heat the same amount of surface. This whole steam arrangement cost me a little over seven hundred dollars.

Some years ago we suggested that a hot pipe be carried up near where the great enemy frost was to be attacked, and not solely along the floor of hot-houses. Many of our florists now have small hot water pipes running along at the foot of the rafters. The idea has crossed the water, although English climate is not so severe on greenhouses as ours. Leading nurserymen have the plan in practice.

I have read with interest the valuable hints on hot water and steam heating by Walter Elder in the Monthly, page 72. I am much pleased to see the subject receive the attention it deserves, in fact, calls for, as it has been an open and interesting question for years whether hot water or steam is to be preferred for heating greenhouses. The question yet remains unsettled, as is fully shown by the many learned and thoroughly experienced advocates of both systems who from time to time give us their experience and opinions.

I hope to again see the subject referred to in your valuable columns, and trust that many of those who have had the opportunity to make experiments may give us their experience. I am fully assured that hundreds of my brethren in the profession, as well as countless amateurs all over the horticultural world, are greedy to learn more of this subject.

But what I wished to refer to more particularly at this time is your remarks appended to that article.

You say "no one has answered why hot-water pipes must be made to ascend. Hot water, as well as cold, will travel faster going down hill." Now, it strikes me that that last sentence settles the much-disputed question forever, and clearly shows why hot-water pipes should not be made to ascend, except where unavoidable. But as the opinion still prevails that they ought to ascend two, four, six or more inches, according to the various theories, in every hundred feet from the boiler, and although I am not prepared to prove or disprove any of the theories, yet I have been constrained by my interest in the subject to submit to you one or two of my experiences in both systems of conducting the water.

Like the majority of my old-country brethren, as well as those of this country, I have, from the time I first gave the subject my attention and until quite recently, been led to belive that in all hot water arrangements the flow must have a gentle and even rise from the boiler to the end of the house orturn-ing point of the pipe, and a like descent from these back to the boiler. In accordance with that "fixed law," I have until lately laid all pipes with great care, and sometimes at a great disadvantage and loss, on that plan. And when I say, with great care, let me add that on whatever plan the pipes may be laid, I have always found it paid to lay them with care, avoiding all unnecessary undulations or bends, as all such, in some measure, tend to obstruct the flow of the water.

As an instance, I will briefly give an experience I had over a year ago. At that time we built a range of greenhouses, five in number. As the opportunity offered I determined to put to the test a plan I had heard of and had often thought of, that of laying the pipes as nearly level as possible. We used the ordinary 4-inch soil pipe, many of the lengths of which are a little bent, consequently the entire line is slightly undulating. The main, a 5-inch pipe, passes along the ends of the houses, under the floor level. At each side of each house an offset raises the water from the main to about twelve inches above that level. From that point the piers or supports for the pipes were built on one level, the pipes being laid on them, the flow above the return, as is customary, each return bend being furnished with a 4-inch air-escape tube.

All being in readiness and the fire started, a gentle warmth was soon perceptible all along the pipes in all the houses, but as the water reached a higher temperature the pipes in several of the lines gradually grew colder, and I immediately concluded that there was air collected at those points where the stoppages occurred. After several attempts to overcome the difficulty, I at last had all the pipes raised at the return ends about two inches (the houses are about 55 feet long), and the air immediately rushed out of the escape pipes, and since then there has been no trouble from that source. The experiment was enough to show me that nothing was to be gained by laying the pipes level, and also that there is indeed very little motive power in hot water, and that what little there is had better be utilized to the best advantage.

Since that time I have become a convert to what we call here the "down-hill plan" of conducting the water. Although very sceptical for along time, I am at last convinced that it is superior to all other plans. I need not here give my reasons for thinking so, as should I, it would simply be to repeat what Mr. S. C. Moon has said in his able article on page 75 of the Monthly.

Although he has not said so, he undoubtedly means the tanks which receives the hot water direct from the boiler to be furnished with a tight-fitting cover; if not, I would beg leave to suggest that a cover should be fitted to the tank to prevent the evaporation of and loss of heat, and that for the escape of air a small 1/4-inch tube be inserted in the cover.

Where a cheaper arrangement may be desirable, a very good substitute for the tank may be had in. a perpendicular 4 or 5-inch pipe, according to the size of the flow. This pipe to be carried up about four or five feet above the level of the top of the supply tank; and, by the way, I have found in practice that the more this tank is elevated above the boiler, and provided the inlet to the boiler be in the return pipe and, I think, better close to the boiler, (a very small tube will answer the purpose) the better will be the flow. But to return to the upright pipe. At about one foot below the bottom level of the supply tank, in this pipe let there be inserted a tee, to which the main is attached, dropped from that point as may be necessary or desirable. The air as it rises from the boiler will float to the surface of the water in the upright pipe and escape, and the water will pass off at the side outlet comparatively free of air.

Last summer one of our florist firms in town made an addition to their establishment by building two more houses, each 10x95 feet, and heated by a 4-inch flow and return pipe on each side of each house. Previous to that, the two small boilers which heat the range seemed to be taxed to their utmost to furnish the necessary heat. It was, however, decided, by way of experiment, to attach to them the additional 800 feet laid on the "down-hill plan." The old pipes are on the old plan. No particular attention was paid to having them at any point on a level with any of the other pipes. The experiment proved much more successful than was ever anticipated. The whole system of pipes now work admirably, all heating simultaneously and evenly, and yet the boilers are not overtaxed. I am confident had those pipes been laid on the old plan, no such satisfactory result would have followed.

But, Mr. Editor, I have already occupied too much of your time; I hope you will excuse me. The subject is one I am fond of talking about, and it is possible I exceed the bounds of patience.

Heating Greenhouses With Steam

Having been very much interested in reading the various articles which have appeared in the Gardeners' Monthly during the last year, and wishing more information on the subject, I would now like to ask those who have had experience the following questions:

How many radiating pipes of one inch or two inch size, are required on each side of a hundred foot greenhouse, and twenty feet wide, to easily keep up a night temperature of 65 when the thermometer goes down to 15 below zero? Are two one-inch pipes as good or better than one two-inch pipe for the purpose of radiating heat? How many-horse power boiler is required to heat such a house (100x20 feet)? Can three or four such houses be heated in the same proportion, that is if it requires a five-horse power boiler to heat one house, will it require a twenty horse power to heat four such houses? Is steam heating cheaper than hot water, regardless of the cost of pipes? Does steam heating work as well in an ascending as it does in a descending pipe, or would the condensation of the steam in the pipes cause trouble in keeping up the circulation of steam in the ascending pipe? Can a steam boiler be safely left at ten o'clock at night until seven o'clock in the morning, or is it necessary to watch it more closely than for hot water boilers ': What style of boiler would you recommend where economy is an important item.

Any one who has had experience in steam heating (for it is experience that we want), that will kindly answer the above questions through the columns of the Gardeners' Monthly, I think will confer a favor on a large number of its readers.