Two years ago I was prevailed upon to give an account of my practical experience in the use of steam-heating of greenhouses, partly urged by-some of my fellow florists, and partly feeling annoyed, to tell the truth, by noticing so many misstatements on the subject appearing in horticultural publications in this country, as well as in England and Germany, most of which evidently bore the stamp of ignorance and prejudice on the part of their authors, while others, in their own description of the apparatus, gave the key to its failure. Had I known the avalanche of inquiring correspondence I was about to precipitate upon myself, I might well have hesitated; but, on the whole, I suppose the thorough agitation which the subject has received ever since, has been of practical benefit to the cause of floriculture. When I can state that at this day every florist's establishment of any considerable size about this city is heated by steam and giving entire satisfaction, and when I am furthermore credibly informed that several other cities are doing scarcely less, I may be justified in the belief that this agitation has borne some fruit already.

It is but a day or two since I met one of our prominent florists, to whom I had given some slight assistance in the shape of advice in regard to steam-heating. It happened to be the day after the most blustering cold night we had this winter, and the enthusiastic endorsement he accorded steam was a caution to skeptics.

The new system (I am only speaking of my own experience with it) has now been on trial seven seasons, and so far it has failed to verify in any one particular the doleful predictions so prevalent at the time when the original bantling began to be talked about. Boilers and pipes have obstinately refused to burst, and the plants grown with aid of steam-heat somehow or 6ther remain distressingly healthy, other treatment being equal, as a matter of course; and what a difference in the attention required ! Let me give an illustration from practical experience in a place, the houses of which formerly were heated by eight hot-water boilers in severe weather. It used to keep one man on the go continually to stoke his fires and watch his thermometers; one or more of the fires requiring to be kept at the greatest attainable draft, while some others performed their allotted duty with less frequent attention. After a night of such labor the man would be completely worn out with being overheated at one time in front of his furnace, and chilled at another in traveling to the next. Now for the contrast.

Instead of eight fires, located perhaps three hundred feet apart, he keeps one; his valves have been regulated for the different temperatures desired on each house, and a week's practice teaches him what pressure of steam he requires to offset any given outside temperature, while his steam-gauge is right before his eye to tell the tale. He takes an occasional glance at his out-door thermometer, and finds, say an exceptional degree of cold, perhaps accompanied by high wind; as a precaution he goes the rounds of his houses and finds old Boreas is getting the upper hand of the fifteen or twenty pounds of steam he may be carrying at the time; that is, he finds 580 where he wants 6o°, or 400 where he desires 450. Does he rush back frantically to stir the fire to greater exertions, or rouse up help to cover the threatened plants with blankets or muslin or paper? Not much he don't; he returns to his boiler and sets the weight of his pressure-regulating valve a few pounds further out, or similarly, if he uses a damper-regulator, he adds a few pounds there, and in the course of a very short time he is absolutely certain to have his houses right to a degree.

Perhaps some of my readers may think the above blanket story overdrawn, but it is not; it happened in my own experience not once, but half a dozen times in one season, not above five miles from New York city, and moreover in what was then and is now one of the best appointed establishments in the country.

If the following information appears lengthy, I wish to offer the excuse that I know the subject to be of some interest to literally hundreds of the readers of the Monthly, as I have their letters to show for. To answer each individually became an utter impossibility, as the scope of questions contained in any single one was so extensive as to require going over the whole field in detail.

To begin with the boiler or boilers most suitable. Nearly every inquiry embraces that, and would be easily enough answered if the kind of fuel most convenient to the respective locality were mentioned. If soft or bituminous coal is your fuel, and your concern is large, say upward of 3,000 feet of glass, I should use the Cornish boiler as the one producing the most economical results; but its first cost is considerably above that of any other pattern. Next in order for the same fuel comes perhaps the so-called Mississippi steamboat boiler, containing a double flue. For anthracite or coke I should give the preference to the following styles of boilers in the order named : 1, locomotive, fire box; 2, tubular, with the fire under the boiler; 3, sectional boiler. The boiler once chosen, the next thing in order is the best location for the same; if the topography of your site admits of a difference in levels, place your boiler at the lowest possible point, so as to be able to return all the condensation to it by gravity; even where your ground will not admit of that altogether, it is of advantage to secure as low a level as possible, inasmuch as the automatic return trap will have to lift the condensation just so much less, and will work at a lower pressure, as it requires about one pound of steam to raise a column of water two feet.

Be careful to secure ample draft by giving your smokestack or chimney an inside area one-third greater than the combined area of the flues or tubes in your boiler, and make your connection from boiler to chimney as direct as possible. As regards the position of the pipes in your houses, be particular to have them hung (which is far preferable to resting them on fixed supports) with a uniform descent to the pipe or pipes conveying the condensation back to the boiler, thereby avoiding the unpleasant cracking noises heard in pipes improperly placed. Make all your connections from the main pipe to the heating coils of uniform size; say 3/4 or 1 inch for very long lines; observe the same rule in your connections with your return pipe, for which, however, you may use a size smaller valve, as, for instance, 1/2 inch valves on return connection to 3/4 inch for live steam, and 3/4 inch valves on returns to 1 inch for live steam.

The relative amount of your radiating surface in your heating pipes to the area to be warmed, of course varies with climate and exposure. For our locality, where the mercury occasionally falls to 200 below zero, and on reasonably well-constructed houses I give the following relative figures:

The size of pipe which I find best adapted to the purpose is 2-inch or larger (wrought iron, of course), designated in the trade as black pipe (lap-welded) and I cannot but repeat my warning against the use of too small pipe, a mistake I have had to persuade against in every new attempt at steam heating; people are led thereto by a notion of supposed economy, than which nothing can be more erroneous. There are two reasons against the use of small pipe on long lines. The first is the rapid condensation going on in comparison with that in large pipe, thus necessitating a much higher initial steam-pressure, and second, the waste of a large percentage of heating power in friction. It would be feasible to convert the steam into electricity instead of heat by carrying it in pipe sufficiently small in diameter.

On the other hand, the introduction of steam as a heating medium in establishments already possessing more or less considerable area of glass heated by the hot-water system, had not unnaturally led a few into an opposite error, that is, to attempt to utilize the existing pipe (4-inch cast iron) to convey the steam therein. In the case of the ordinary soil pipe, generally used for hot water, I do not hesitate to state most emphatically that they are useless for steam, no matter at how low a pressure. I have admitted steam to a line of them at less than half-pound pressure, and had upward of 100 feet of them cracked in an instant. The much heavier pipe made by some manufacturers (Messrs. Hitchings & Co., for instance), may be able to carry steam at low pressure; but I should hesitate about assuming so great a risk; and why should you do so when there are several ways out of the difficulty? In the first place, by taking your pipe apart, you may realize, as has been done here, to my knowledge, almost if not quite sufficient to pay for a complete outfit of steam apparatus.

Should your pipe, however, be joined with iron filings, and therefore too troublesome to take apart, I should advise the adoption of the method described by Messrs. R. G. Parker & Co., of Boston (Sept. No. G. M., 1880), that is, to heat the water in your pipes by steam through a coil introduced in place of your respective hot water boilers. You will thereby enjoy nearly all the advantages of the steam system, and may of course use direct steam-heating apparatus in any additional houses, while firing the entire establishment from one point.

To mention a few other points suggested through the correspondence arising on the subject, and which I shall touch as briefly as possible : Capacity of boiler in horse powers. From my experience I should advise one-horse power for each 120 square feet of radiating surface, which in two-inch pipe is about 240 lineal feet; but I consider liberality on that point a wise economy. Another point of advice is to rather use two boilers placed in battery, but in such a way as to be able to use but one at a time or both together, as circumstances require. Be sure to provide both ample steam and water connection (4-inch or more), for reasons it would take too long to explain, but is nevertheless of greatest importance.

The advantage of being able to return the condensation to the boiler is so great, not only regarded from the standpoint of economy in fuel, that I venture to allude to it again; much the same as Mr. Peter Henderson, referring so frequently to the importance of firming the soil about seeds because of its great importance. In addition to effecting a most decided economy in fuel, it insures freedom from scale or mud deposits in the boiler, because the same water is used over and over again. It also insures you from the danger arising from a sudden stoppage of your water supply, caused by freezing, or perhaps a break in the water pipe which supplies you, and which would leave your boiler dry before you could devise any means to prevent such a mishap; in short, my urgent advice is, not to neglect this point above all others. I regard all other devices for the better control of steam as a heating medium, highly valuable as some of them undoubtedly are, as secondary to the absolute and constant return of the condensation to the boiler.

Of these above devices I would mention as very desirable a good damper-regulator; its name sufficiently describes its use; also a reliable pressure-regulating valve, which will keep the steam in your heating pipes at any uniform pressure you may want (thus guarding against overheating through carelessness) as long as you maintain as much or more pressure in your boiler.

Such safety-guards are not only of great assistance in the uniformly even performance of the entire apparatus, but they also effect a very noticeable saving in fuel.

I believe this covers the principal points of the inquiries I have had on the subject. I have tried to avoid the use of technical terms as much as possible, so as to be intelligible to those of your readers not mechanics enough to grasp their meaning. If I have succeeded in making myself understood I shall feel amply paid for the effort.