I have frequently been spoken to by friends to give people interested in horticultural progress, and especially in the construction and heating of greenhouses, the benefit of the results obtained by my method of heating greenhouses by low-pressure steam.

As the last two numbers of the Monthly contain articles on the subject, or rather against the practicability of that mode of heating, by Mr. Josiah Salter, of Rochester, N. Y , I thought best to take up Mr. Salter's arguments point by point, and prove their entire fallacy by actual results obtained during four continued seasons in one instance, and two seasons in another, on a scale sufficiently extensive to prove what I claim, viz., that a properly constructed heating apparatus by low-pressure steam is: first, absolutely safe; second, far more efficient than any other; third, economical of fuel as against any other; fourth, economical of attention, neither requiring an engineer, nor even as much attention as the hot water system; fifth, in cleanliness it will compare favorably with any other mode; sixth, one of the greatest of its merits is the ease of regulation to any desired temperature to a degree which we know no other mode of heating is capable of; so much so, that you may keep any number of houses, each at a different degree of temperature from any other, though all heated by one boiler; seventh, that the quality and health of the plants grown by low pressure steam challenge comparison with those grown by any other method; eighth, that you can heat any quantity of glass, no matter how uneven the levels of your houses, or whether they are connected or not, from one central point; ninth, that with all the forementioned points in favor of low-pressure steam, the first cost of the apparatus is considerably less than that of any good hot water apparatus able to do the same work, which difference increases with the extent of the space to be heated; or in other words, the greater the amount of heating to be done, the greater the saving in first cost of apparatus as compared to hot-water.

Before I proceed to substantiate and prove the above-mentioned points, let me state some actual results obtained. In the fall of 1876 I built the first of my low-pressure steam apparatus for the greenhouses now operated by Messrs. R. C. Patterson & Bro., on Ellsworth av., of this city; they contain 9000 feet of glass, all with one exception low span-roof houses, 12 feet wide, 7 feet high at ridge-pole, walls about 3 1/2 to 4 feet high, used for general assortment of bedding plants; one house 50 feet long, 12 feet wide, about 11 feet high, used for tall plants, smilax, etc. About one-half of the above area is kept in winter at a temperature of 45° to 50°, the balance from 60° upward. This has stood four seasons' use without the expenditure of one cent for repairs, excepting the replacing of a smoke stack by a brick chimney; it has been operated from first to last by ordinarily intelligent greenhouse hands; it has from the beginning worked like a charm; the plants sent out from the establishment certainly invite comparison, and the amount of fuel has been so trifling that the Messrs. Patterson have not thought it worth while to use any device for taking the condensed steam back to the boiler, (a sixteen horse power tubular) continually wasting the same into the sewer while taking a steady stream of cold water into the boiler to replace the condensation.

The establishment consumed forty-five tons of bituminous coal (principally nut coal and slack) at a cost of $95.00 during the season of '79 and '80; in an ordinary severe season they use of course proportionately more, and from 00 to 70 tons of bituminous coal is probably a high average.

During 1878, I erected the establishment now owned and operated by Messrs. A. R. Reneman & Bro., of this city, it contains upward of 30.000 feet of glass, constructed as follows:

Five low span-roof houses 12 x 100, 7\ feet high under ridge-pole; three forcing houses, each 24 x 132 feet, built on a side hill, one above the other, about 12 feet high under ridge-pole; one house 24 x 112, built on terraces with the grade of the hill, will average 14 feet high; one low house 10 x 132 feet; one low house 6 x 132 feet. This concern makes a specialty of growing cut flowers, and devotes large areas to stove plants and others requiring a high temperature so that about two-thirds of the whole space had to be supplied with pipe sufficient to maintain at least 55° in the coldest weather. It contains in round numbers 7,000 feet of two inch pipe, all heated by boiler (a fifty horse power ordinary locomotive boiler). As in the other case, it has been operated by ordinary greenhouse hands, never requiring the service of an expert; and the products of the establishment, both plants and cut-flowers, invite comparison, and are a credit to the intelligent management of Mr. F. Wuttke, who has been in charge almost from the beginning.

This apparatus is supplied with a device for returning the condensation to the boiler, which it does automatically and without the slightest attention from any one, although a large portion of the heating pipes are below the water level of the boiler. It is not supplied with any damper-regulator or other device to regulate or feed itself during the night, for the simple reason that it was thought unwise to leave such an establishment without a watchman at any time; as it is, it will compare favorably with any other apparatus as to economy of attention.

The cost of this apparatus was much less than two-thirds the cost of hot water as per price-lists and discounts obtained at the time.

The amount of fuel used during the season of 79 and '80, as per account of the superintendent Mr. Wuttke, was 4,000 bushels of bituminous nut coal, equal to 152 net tons, or 135 gross tons; or in an ordinary severe winter, about 200 gross tons, at an average price for coal here of 7 cents per bushel. Every square yard of plant growing space (that is counting only the area of the benches and beds, and not that occupied by walks) is heated by an expense for fuel of 20 cents for the whole season.

After giving the above actual results, obtained through several seasons, which practical men will consider worth any amount of theories whether pro or con, I will endeavor to show Mr. Salter where his theories as to the unsuitability of steam as a heating medium are at fault. I hope I need hardly say to Mr. S. that in doing so I am only trying to respond to his invitation to elicit information on the subject.

Mr. S. admits that probably heat might be gotten up more quickly to a certain degree by steam than by hot water, though he thinks that the effects of the fire will be felt sooner by the latter method. How much heat will Mr. S. get out of his water pipes in, say thirty minutes after starting the fire? It takes about that time to raise fifteen pounds of steam in the fifty horse power boiler above referred to, after which, by opening one valve you have your heating pipes hot in two or three minutes I doubt if Mr. S. would have his fires started thoroughly in all the boilers which would be necessary to heat the concern by hot water by the time you can raise the temperature in all the eleven houses of Rene-mans five degrees.

Now as to one of the most frequent queries in regard to the kind of heat obtained by steam, I wish to say that the amount of misconception on • that point even among professionals is something wonderful. Isn't the heat obtained by steampipes too dry for plants? This is the question asked with almost never failing regularity, and my answer is, no, and a thousand times no. Heat, per se, has nothing whatever to do with moisture; you will get as much moisture out of a cast-iron hot-water pipe as you will out of a powder-horn or out of a steam pipe; what moisture you want in the atmosphere of your greenhouse you must apply externally, and you do so apply it, whenever you feel the air too dry, by syringing or watering, wherein the steam heating has the great advantage that you can restore the desired moisture in the shape of a vapor bath, which comes nearer nature's own operation of dew for the same purpose, and which process the most delicate plants delight in to the highest degree, when they would be positively injured by ever so gentle syringing.

You will dry up the atmosphere of your houses precisely to the same extent, no matter which heating medium you use, according to the temperature you maintain, no more with steam and no less with hot water.

As for the gift of continuance of our heating medium I readily admit, that should our fire go out and the boiler cease to make steam, the temperature of the house would fall very rapidly, certainly more so than if heated by hot water, but steam is capable of being regulated to the fraction of a pound by automatic devices, which hot water is not; and as for the fire going out for the want of fuel, has Mr. S. never heard of the Magazine Base-Burning Stove, which may be safely left for ten or twelve hours with the certainty of finding a pretty good fire at the end of twenty?

Again Mr. S., says steam is not simple enough and not to be trusted to the care of boys or laboring men without danger of condensing or bursting, while any possible mishaps to the hot water system would be mere trifles. My experience as a florist is precisely the opposite, and I dare say I stand by no means alone. I have had hot water pipes burst so seriously that the repairs necessitated the complete stoppage of circulation, in fact the emptying of the pipes, and the mere good fortune of a mild spell of weather at the time, alone saved the contents of 12,000 feet of glass from utter destruction. Now suppose such an accident, however unlikely, had occurred to steam apparatus, what would have been the consequence? You would merely shut off that one pipe by its supply and condense valves, take apart the nearest union and repair the damage at your leisure, while all the other pipes in your house are working just as usual. We do occasionally hear of steam pipes bursting under high pressure, but have you ever heard of any doing so at a pressure of 20 or 30 pounds, (which you seldom exceed in the most bitterly cold weather) when they are or ought to be tested to at least 150 pounds?

Your boy or laboring man cannot neglect his duty without receiving a warning. If you cannot trust his intelligence, let your foreman or yourself set the damper-regulator to whatever pressure experience will teach you is necessary for a certain temperature, see that your magazine is filled, and he can do no mischief except by intentional malice, against which, your hot water apparatus is as little proof as any other.

With steam heating you are absolutely in the position to laugh at Jack Frost, while with hot water, unless you put in far more pipe than you need in average cold weather, you are at the end of your string when you bring your water to the boiling point. With steam you simply add a pound or two more to the pressure with the comfortable assurance of a snug little reserve force of forty or fifty pounds, which you may use with perfect safety, but which are never called upon. Mr. S. says that steam has never proved effectual for horticultural purposes, as far as he knows, and has been abandoned wherever tried. I venture to say without fear of contradiction, that in every such instance (and 1 have heard of one myself through Mr. Peter Henderson) the cause could be plainly demonstrated to be a violation of quite well understood scientific principles in the construction of such apparatus. I know of two extensive florists' establishments in Chicago heated by steam, giving entire satisfaction, although they were, in my opinion, far from being perfect in construction I might easily still more enlarge upon the advantage of steam over hot water, but I feel this communication is already much longer than I intended, and for which Mr. Editor, I crave indulgence both from yourself and your army of readers.