Would it not be better, in giving number of feet heated, either by flue, hot water or steam, to have it always understood to be "cubic feet?" These can be readily ascertained, no matter what the shape of the roof. The rule for heating by hot water, is "one foot of 4-inch pipe to three or four square feet of glass in the house (roof, side and ends)." While by steam the rule is, "one square foot of radiation, (say two feet, 2-inch pipe,) for thirty, forty or fifty cubic feet of air, according to the temperature (outside) of where the house is located." North, less number of cubic feet; South, greater number of cubic feet.

In making comparisons of heating, by either method, the location and degrees of outside temperature must be taken into consideration, also the attention paid to firing.

A great many seem to think that firing, is simply "firing" on coal and taking up ashes, but it is more than that. To maintain a proper fire, is an art that most of us seem to forget, or have never learned.

Now, if steam is much the better heating medium for dwellings, stores, halls, etc, where humanity dwells; is a more gentle, equable temper-ature, easier controlled, less attention required, more economical, why will not these points hold good for its use in heating houses for living plants?

My experience with steam and "Dunning Boiler" (self-feed), for the past two seasons, does not make me wish to change back to hot water, which I used ten seasons. Jan. 4, 1886.

Mr. N. B. Stoever writes, that he calculates the number of feet of glass by the number of feet in the boxes used for glazing. To Mr. Hippard's houses 250 boxes were used; in this way he calculates 12,000 feet. The way in which the glass is used would enable 25,000 feet to be used in this way instead of 12,000. He believes that the proper way to understand " feet of glass " is by the number of feet of glass used, and not the amount of ground covered by glass or the number of cubic feet enclosed by glass.

In regard to the price of coal, Mr. Hippard pays by the car load for slack 80 cents per ton, and is delivered in the bin at the establishment at from 20 to 22, costing just about $1, and not $1.25 as stated by "Ohioan".

Mr. Stoever further suggests that if lump coal is the cheapest, as "Ohioan" believes, one might suppose the Youngstown works would use it for their steam boilers.

We have had to condense Mr. Stoever's letter because much of it has not reference to the matter of what is to be understood as "feet of glass" in calculating the work of a steam boiler, which was the chief question raised in our columns.

Since the columns of your valuable and instructive magazine are becoming somewhat interesting in the direction of cheap greenhouse heating by steam, we consider it our duty to offer in evidence, our success and practical knowledge. In regard to Mr. Stover's article concerning the heating of Mr. Hippard's establishment at Youngs-town, Ohio, we have this much to say. That we have been to see his place, which we consider one of the finest commercial establishments in this country, not only in structure, but stock and everything connected. The size of his place is, we think, fully what Mr. Stover claims for it. We are about to add to our place, Mr. Hippard's novel invention, that cannot help but become a necessary article connected with steam heating. The apparatus is an alarm bell which can be adjusted to any pressure desired, by moving a weight; and when it is set, say at one pound of steam or less, and the steam comes below that pressure, it rings the alarm and wakens the fireman who may have accidentally fallen asleep, thus avoiding - unusual occurrence - chilling or freezing the plants.

In regard to our establishment, we will say this much. That we have 8,000 square feet of glass surface. That we heat with a small 10 horse power locomotive boiler. Attached to it we have over 3.500 lineal feet of 1 1/4 inch gas pipe. Our fuel is what is brought out of the mine, called run of the mine; and according to what we have thus far used, we will consume about forty tons, at a cost of $1.25 per ton, delivered at our place. However, our apparatus did not give us any satisfaction whatever, and we commenced to correspond with Mr. H.; and he gave us drawings, but could not get the results necessary, until on last Thanksgiving Day we called upon Mr. H. at his place, and went home with some points; and have now, we consider, as nice a working steam apparatus as we can wish for. Everything is working like a charm. We found Mr. H. a florist among florists. For all of his trouble making drafts and corresponding, he would not allow us to contribute one cent towards his expense and trouble. Such generous men are bound to win, if generosity has anything to do with success.

Cumberland, Md., January 30th, 1886.

I have read with interest the articles on steam heating of greenhouses, in your valuable columns. I will give your readers my experience in that line. To begin with: The boiler should be of sufficient size so as not to crowd it. There is nothing gained and fuel wasted by having the boiler too small. It should have I square foot of fire surface to 30 feet of glass, where the mercury gets 200 below zero, or more. For distributing the heat, 1 1/4-inch pipe is the best size to use. It should be distributed over the space to be heated as much as possible. 2 feet 8 inches of 1 1/4-inch pipe makes a square foot of heating surface; it will heat 5 feet of glass, and should be so arranged that half of the heating surface in each house can be shut off in mild weather. The steam supply to each house should be run about 18 inches from the ridge, this keeps the glass thawed and lets the sun in sooner.

The main supply pipe from the boiler should have 3/4 of an inch sectional area to each 100 feet of heating surface; and be reduced in proportion as the branch supplies are taken off. The ends of the supply for each house should have a drip of 3/4-inch pipe connected to the return pipe below water level of the boiler. The return pipes should be one size smaller than the supply pipe, and dropped below the water level at the nearest point possible. All the heating pipes and returns should fall 1 inch in 10 feet to the boiler. At the end of each coil put an automatic air valve to let the air escape. An apparatus constructed with these rules in view, cannot fail to give the possessor entire satisfaction, and he can safely leave his fire 5 hours in the coldest of weather; and with a saving of 25 per cent. in first cost, and use less fuel than hot water.

These figures are based on practical experience of myself and others in various parts of the country. The sizes of boilers and heating surface will admit of a reduction, 10,000 feet of glass and over, where the houses are built close together.

At some future time, I will give your readers some facts and figures on steam as a heating agent in heating water in the original plant of hot water pipes.

A book on Steam Heating

By A. B. Fowler, Exeter, N. H. Mr. Fowler is well known to our readers by his excellent contributions on "Steam Heating." This is a pamphlet treating of hot water as well as of steam heating, and will be found of great value to all who may want to erect glass-houses of any kind, as well as those who may wish to learn of the great progress made in greenhouse heating.