I have been making some inquiries, by mail, of florists, covering the country from Bangor, Me.-to Baltimore, Md., and from the Atlantic to Chicago, 111., hoping thereby to obtain the practical facts regarding the comparative merits of steam and hot water as heating mediums for greenhouses. Responses to my inquiries establish the following facts, viz.: During the past winter one ton of coal burned in a hot water apparatus has heated 108 sq. ft. of ground covered by glass to a temperature of 531/30. One ton of coal burned in a steam apparatus has heated 149 sq. ft. of ground covered by glass to a temperature of 60¾. The questions submitted to those using hot water were identical to those sent to users of steam, and while the hot water apparatus were of all the different kinds, those of steam were all of one kind, "Exeter".

I do not know of any method of combining these results, so as to bring into simple form the comparative value of one ton of coal in either apparatus, but submit what information has been gained for the benefit of those interested, if you choose to publish it. Exeter, N. H.

[We suppose a very large number of comparisons might give data from which we might get an average; but averages are dangerous in calculations of this kind. The heating of a house very often depends as much on the setting of a boiler by the mason, as on the actual heating capacity of the boiler and pipes. The glazing of a house has an influence, and the velocity of the wind in connection with outside temperature will make the inside vary immensely. As a question of physics, it takes more coal to heat a certain amount of water to the condition of steam, and to keep it to the condition of steam, than it does to warm water; and if people could only persuade themselves to let the warm water run down hill, as long ago advocated by Mr. William Saunders of Washington, instead of the silly practice of forcing it up hill as everywhere prevails, we should have a much better showing for hot water than the figures collected by Mr. Fowler can possibly show. But though it must take more coal to make steam than hot water, there are so many counterbalancing advantages for steam in many instances, especially for heating large establishments, that it is better in these cases than hot water. - Ed. G. M].

In your remarks at the close of an article with the above heading, July number, I notice you say " As a quest on of physics, it takes more coal to heat a certain amount of water to a condition of steam and keep it to a condition of steam than it does to warm water".

Now, Mr. Editor, I think your statement a little misleading. You say, a certain amount of water. Well, I will call this certain amount of water 50 gallons for steam and 50 for hot water. That is, a certain amount for each apparatus if I have your meaning of it. Now of course it will take less to heat this water to the usual temperature in a greenhouse circulation which will average about 1900 than what it would to make steam. But is that a comparison ? I should say not. Now let me put this in a light that will be more easily understood. In a good steam boiler 1 have 50 gallons of water, sufficient to raise steam to fill the whole system of circulation. In order to heat by hot water all the circulation must be full and the proportion for hot water would be 500 gallons. Now we start a fire in the hot water boiler and let it run full force, and in two hours we have the water to a boiling point in the boiler and about half-way through the circulation. In the steam boiler the water can be brought to a boil in twenty minutes, and in ten more the whole system of pipes can be brought to 2120, and at a pressure of two pounds the diaft will be shut off and the fire only consumed fast enough to maintain the pressure.

With the steam there is no heat for the first twenty minutes, and but little from the hot water, but at the end of two hours the steam boiler is turning out the greatest quantity of heat and working with drafts closed, while the hot water boiler is burning its coal without hindrance. The steam boiler has been under check for one and a half hours.

My experience has been that it takes one-third more coal to heat a dwelling house by hot water than by steam; and if true in this why not in greenhouse heating ? With proper adjustments steam is the most economical method of heating a greenhouse, and can be left alone for a longer time than any hot water boiler. Norwich, Conn.

[There is not probably much difference between our correspondent and us. The difference is chiefly in the expression of the same idea.

Our chief desire was to impress on the reader a fact obvious enough in itself, yet apt to be forgotten in discussions, that heat can only come from fuel, that the shape of boilers, or form of the water (as steam or the ordinary liquid) adds nothing to the quantity of heat in a given amount of fuel. We must increase fuel to increase heat. It certainly does take less coal to merely " warm " 50 gallons of water than to make steam of it; and yet the point made by our correspondent, that a dwelling house can be heated for one-third less cost by steam than by hot water, be perfectly correct. But this comes from the more ready distribution of the heat, as we understand it, and not from " economy in fuel,." as so generally contended for.

Practically, as we have said, it is but the expression of the same idea, but we have often seen that a correct statement of a principle is by far the best path to the understanding of that which depends on it. - Ed. G. M].