Dear Sir, - J have read, with much interest, the discussion of the boiler question which has taken place in the Horticulturist since you published my article on Heating Apparatus for Horticultural Glass-houses, in March last, and find no proof worthy of notice to contradict my statement, as to the double cone boiler of Weathered & Oherevoy being the best with which I had been acquainted. It appears, however, that Mr. James H. Park, of Brooklyn, does not so think, if we are to judge from his remarks on page 585 of your present issue. In these remarks he admits that "an article in the July number of the Horticulturist, in which the heating apparatus put in for me by Weathered and Cherevoy is so accurately described by your correspondent "B.' that I am satisfied, beyond doubt, that my place is referred to, as there is nothing else in Brooklyn approaching his description." And he further writes: "I was compelled to stay up nightly until midnight, in cold weather, while my man had to be on hand at five in the morning, to keep my plants from freezing; the thermometer being often, in one house, at 38°, and in the other at 42°." This gentleman " B." says: " A very skillful gardener in this city does business in a house one hundred and thirty feet in length, of an L shape, sixty feet of which is span roof, twenty-two feet wide, ten feet high; the remaining seventy feet is lean-to, fourteen feet wide, and same height;" and further on, "he makes the water boil . . with No. 4 of the saddle and conical boiler, and five hundred and twenty-six feet of four-inch pipe".

Now, as Mr. Park has endorsed, over his own signature, all that "B.," as above stated, has written, there must be something requiring further explanation before this boiler ought to be condemned. Let us examine how the case stands concerning his peculiar position and requirements, and whether or no the boiler is at fault In this* example we have a No. 4 boiler, and five hundred and twenty-six feet of pipe; the makers guaranty this size to boil the water with five hundred feet of four-inch pipe, and I have seen Mr. Park's own acknowledgment, in writing, that the water was made to boil in his. This is all that is claimed for the principle, either with this or any other model, (excepting on the dangerous high-pressure plan;) consequently, there must be an error somewhere else. A trifling calculation may, perhaps, plainly show up the delinquency.

The height of the upright front of these two compartments is not given, but it is not likely to be less than five feet; accepting it at that, whether inside or outside matters not materially, and we have a cubic bulk of about nineteen thousand two hundred and ten feet of air to be warmed by the pipes. Considering that in the coldest night 45° be required in the span-roofed, and 50° to 55° in the lean-to, unless in a most extraordinarily sheltered situation, there ought to be not less than one lineal foot of four-inch pipe to every twenty cubic feet in the house, which, according to the above measurement, will amount to nine hundred and sixty and a half feet of pipe; and, as this comparative calculation is a demonstrated fact to all persons of proper experience, it is readily seen where Mr. Park's failure is. The thing speaks for itself so far. A large (No. 5) boiler, and corresponding length of pipe, are absolutely necessary.

With regard to the constant attention required, which Mr. P. complains of I have to speak very differently, and can not see how, or under what circumstances, the fire can not be left over five hours. During the whole of last winter, and so far in this, we have had here a No. 3 (one size smaller than the above mentioned) boiler of this make to work, and it warms, satisfactorily, a Camellia house seventy-eight feet long, twelve feet wide, and fourteen feet high, facing W.N. W., and on an exposed hill When the weather is not severe, the fire is not even drawn out of the furnace oftener than once a week; and with the most intense frost, about every third or fourth day. The only attention given, is to rake down of an evening, filling up well with coals at the same time; the door is then closed for fifteen minutes, when the heat is up; the damper and ash-pit are now partly closed, according as the draft of the outside wind is quick or slow. Nothing further is needed until morning, although we occasionally throw on one or two shovelfuls of coal at nine or ten o'clock P. M.; but this latter is only a matter of extra caution, and, generally, might be dispensed with.

In the morning the door is thrown open, the ash-pit entirely, and the damper nearly closed, and thus the remaining fire slumbers along till evening again. Of this, Mr. P., or any other person, may have ocular demonstration, if they feel so inclined. The quantity of coals consumed by this boiler, from the beginning of November till the middle of April, is not over six tons, and the temperature is bo steady that I will guaranty to tell, before entering the house, within 2°, what the thermometer registers at three in the morning.

I hope, Mr. Editor, that this important subject may be discussed in a friendly spirit, until we all know which is the best boiler in existence. Let each one put his name to his article, as evidence of his good faith. For myself, I speak without fear or favor of any person; and again repeat, after over thirty years' experience, that none has given so much satisfaction as the above mentioned.

Yours most respectfully, Wm. Chorlton.

[Mr. Chorlton treats the subject in a practical, common-sense way. Those who have boilers may gather some useful hints from the above. It is something to know when we have got a good boiler, but more to know how to manage it; and just here, we think, a great many fail. In discussing a subject of this kind, we want to know the length, breadth, and height of the house; the length and size of pipe; the quantity of coal consumed; and other matters of this kind, all of which sensibly affect the results. Something like a true test might be reached by attaching different boilers to the same, range of pipe, and noting the quantity of coal consumed by each in a given time, the average temperature, etc.; the condition of the atmosphere outside to be the same in all the trials. The structure of houses varies so much, that four hundred feet of pipe may be sufficient to heat one of given dimensions, and five hundred be insufficient for another of precisely the same size. Exposure, too, exercises an important influence, as do many other things not commonly thought of; so that some such test as we have mentioned above would seem to be needful to give us results approximating to the truth. - Ed].

Babylon, L. L, December I7, 1860.