Dear Sir: - "a Reader" in the June number of the Horticulturist, page 291, asks for "facts and figures" on the efficiency of hot water boilers in statements addressed to you on the subject. Having sent you a communication on the saddle and conical boiler, which you had the kindness to publish in the May number, and to which he refers, I willingly state what I know on the subject.

As to the dimensions of the house, asked for by your correspondent, the slightest reflection will show him that there is no given rule on this point; in the present state of horticultural architecture, when no two men build alike, there can not be any. An amateur of means builds a house of taste and elegance, which is so far away from that which an intelligent practical gardener would build for his own use on the same area, that the practical man will heat his house and produce a better result with half the means which the owner of the more expensive structure would, and must of necessity, expend for his purpose.

I built my greenhouse three-quarter span, 130 feet long, 16 feet wide, 9 feet high in the centre, on the south side of my garden fence; back wall planked and filled in with brick on edge, 6 feet high, front wall two feet high, back rafters 4 1/2 feet, front rafters 12 feet; sash bars on the fixed principle; ventilators over the ridge plate, as at Bridgeman's, 876 Broadway, New York; and yet practical men have told me that my house is not "half tight" - that to exclude the north wind and its consequences, I should have built the back wall of concrete eighteen inches thick, or a hollow brick wall of the same size. I know I could thus make a "tighter " house, but I know that the "practical men" are few in number who build alike, or pay the slightest attention to the laws of light and beat in horticultural buildings; and therefore it is, that the means that would heat one house, would not keep the frost out of another of the same size, in different hands.

A very skilful gardener in this city does business in a house 130 feet in length, of an L shape, 60 feet of which is span roof, 22 feet wide, 10 feet high; the remaining 70 feet is lean-to, 14 feet wide, and same height; the whole so loosely built as to do injustice to any mode of heating. It would do you good to walk into it in winter, in your flight from the wrath to come outside. He makes the water boil, and keeps a high temperature in this extent of house, in time* thai try men's souls, with No. 4 of the saddle and conical boiler and 526 feet of 4-inch pipe. The quantity of coal burned from November to May was 8 torn, and when he had trimmed his lamp at night, he says he had no occasion to look to it until morning. I put this case as the worst I can find, against the saddle and conical boiler.

If your correspondent were a practical machinist, disposed to investigate matters every day under his eye, and engaged in the construction of boilers for horticultural purposes, I should most willingly submit to his consideration a few "opinions," a careful and intelligent investigation of which would lead to useful" facts and figures " touching his business; but as I take him to handle the hoe and rake as I do, with a view to oblige him I have called on Messrs. Weathered and Cherevoy, 117 Prince Street, New York, the makers and patentees of the saddle and conical boiler referred to, and they assure me they warrant their boilers with the following powers, assuming that the greenhouse is carefully and closely built, and not over 12 feet high. They also add that they have lately patented a boiler of greater power.

No. 5. Largest size, grate surface, 19 inches diameter, 283 square inches, will heat 800 feet of 4-inch pipe containing 434 gallons of water.

No. 4. Grate surface, 15 inches diameter, 176 square inches, will heat 500 feet of 4-inch pipe, 271 gallons of water.

No. 3. Grate surface, 12 1/2 inches diameter, 122 square inches, will heat 300 feet of 4-inch pipe, 163 gallons of water.

No. 2. Grate surface, 9 inches diameter, 63 square inches, will heat 150 feet 4-inch pipe, 82 gallons of water.

No. 1. (Not yet constructed).

To the makers of this very excellent boiler, I beg to refer any who wish further inquiry on the subject.

It may be useful to state, that 100 feet of 4-inch pipe contains 54 gallons of water; that 100 feet of 3-inch pipe contains 30 gallons; that 100 feet of 4-inch pipe is equal in effect to about 150 feet of 3-inch pipe, the capacity being in all cases in direct proportion to the square of the diameter of the pipe. Your obedient servant, B., of Brooklyn.

[In our next we shall give a letter on other boilers. - Ed].

Editor of the Horticulturist: - I tried last fall, and again this spring, to secure a supply of Wilson's strawberries. The first hundred failed; of the second hundred, I have saved some fifteen. They were all from Rochester. So I am almost disheartened in the attempt at getting them from abroad. But, as I see that you are to have an exhibition of the Austin at the office of your valuable paper this season, I will have to call into requisition your judgment about its value. If the berry is really what it purports to be, and you think you can send me one dozen safely by mail, you will confer a favor by doing so at the right time.

I have a very fine grapevine, which was taken from the roots of an old one which had been transplanted and died. The name I do not know. The bunches are long, heavily shouldered, bright red; the vine a luxuriant grower, a brownish color, leaves very large - lobed and sub-lobed - villous underneath, and very much wrinkled, and deep green on upper part. This vine bloomed last season very finely, and again this spring, but will not set any fruit. Why is it? It does not bloom for more than three weeks after my other vines. Let me know what is the matter, and how to remedy the evil.

Some of the very finest nectarines I have, when half-grown, wilt and fall off. I have a Stanwick, very young; it showed fine bloom, and set three nectarines, the largest of which, when nearly as large as a common hen's egg, wilted in forty-eight hours, without any apparent cause, and fell off; the other two seem to be doing finely. Why is this? The Stanwick seems to do well with me out-doors, better than a great number of other nectarines, and the finer peaches.

But I do not understand this wilting of the Boston, Downton, and Stan wick. Why is it?

Yours truly, in great haste, M. S. Frienon.

Columbia, May 26, 1860.

P. S. - Does the striped bug, that is to injurious to cucumbers and other vines, ever attack the nectarine? I find them in large numbers on the Boston, and the skin sometimes scarred. Is it these bugs? It is not the curculio.

[Only 15 out of 200 Wilson's Seedling! There must be something wrong with such results. What is the nature of your soil, and how did you prepare it? - We have seen the Austin, but think it would not suit you. It is large, but deficient in flavor. - We can not tell, from your description, what is the matter with your vine. Having been propagated from a fruitful vine, it ought to be fruitful like its parent. Are the flowers defective? Let us know how, and where, and in what you planted the vine. - The wilting and dropping of your nectarines we suppose to be caused by either the borer or the curculio, but probably the latter. But we suspect you have been applying some artificial fertilizer to your soil which has had much to do with all your difficulties. - Glad to hear that the Stanwick does so well with you; you can not plant anything better in that way. - The "striped bug" does sometimes attack both the Nectarine and the Peach. Try the Gishurst Compound on your insect enemies. - Ed].