various parts of the country.

We do not propose, in our present work, to enter upon the investigation and discussion of the various theories of heat, light, color, radiation, &c., which properly belong to scientific treatises on these subjects. We intend to give only practical examples and results, from an extensive professional experience, with numerous designs and plans of buildings, most of which are now in successful operation, with the expectation that this volume will contribute not only to the general information of our horticulturists, and of gentlemen who are establishing themselves in the country, but also to create and encourage a taste for this kind of culture of exotic and delicate fruits, as well as the exquisite but tender gems of the floral world. When we find that we can command, at comparatively small cost of money and attention, the beautiful and luscious fruits of southern and tropical climes—their rarest and choicest flowers—the most delicious grapes, the finest peaches, nectarines, and apricots, the fig, and the pineapple, if we will; and that we can command these in abundance, to load and adorn our tables daily, the time cannot be distant when horticultural buildings, of various descriptions, will be found on all our country places or attached to our city homes.

POSITION OF HOUSES.

For lean-to or single-roofed structures used as forcing-houses for grapes or other fruits or plants, a southern aspect is generally preferred. Our own preference would be a position facing South-East, on account of the advantage gained from the morning sun, which is so favorable to the health and growth of all descriptions of plants. Although an hour or two of the evening sun might be lost to a building in this position, yet the rays are then comparatively feeble, and this loss would be much more than compensated by the more genial morning light.

Cold Graperies, with span roofs, and glazed at both ends, are better placed North and South,—that is, with the ends facing these points,—as nearly as a due regard to the positions of other buildings in the vicinity, and the general symmetry and apportionment of the grounds will permit. Each side of the roof will thus receive an equal amount of sun-light. For span-roofed Green-houses the rule is not so arbitrary, the glass not being lined with foliage, as in the case of graperies, the diffusion of light would not be materially obstructed. Under some circumstances, Green-houses may be placed east and west, as when a portion of the house is to be devoted to the purposes of propagation. The north side can thus be advantageously used, being less exposed to the sun's rays. Many plants requiring partial shade, would find there, also, the most favorable conditions for their cultivation.

Green-houses or Conservatories attached to dwellings, will answer in almost any position that convenience may require, or the taste suggest, as they are generally not so much intended for the growth of plants as for their display when in bloom. The sun should shine upon them, however, at least half the day. When they are intended for the growth of plants, then the more sun-light they can have the better.

FORMS OF HOUSES.

Until within a few years past, the straight-pitched roof, both single and double, has been used almost exclusively in the construction of glass houses. That there is an advantage in this form over some others, on the score of expense, and because there is less skill required in the builder, we admit, but there the advantage ends. The superiority of the curvilinear form is now beginning to be very generally acknowledged, on account of its being more graceful and pleasing to the eye, and because of its superior adaptability to the growth of plants. When to the curved roof is added the further improvement of circular ends, as illustrated in some of the designs furnished in this work, we have secured forms of houses that will admit double the light of the old-fashioned, heavy sliding sash structures which were built twenty-five years ago. Happily these old glass houses are fast falling into decay, and but few new ones are erected on their model.

Curvilinear roofs possess advantages over those of a straight pitch which may be briefly summed up as follows:

1. A larger run of roof for a given width of house, and consequently, more and better diffusion of light.

2. A greater power of reflecting the sun's rays, because of the constantly varying angle at which they strike the glass.

3. A greater amount of head room within the building, without the necessity of high parapet walls, or perpendicular sides.

4. Greater strength of the roof, enabling it to resist pressure from accumulated snows, without the necessity of supporting columns under the rafters, which are indispensible under a straight roof of considerable span, to prevent its settling down, and the opening of joints in glass and wood work, admitting the cold air from without.

A good proportion for a grapery or conservatory, is twenty feet in width by fifty feet in length. We think the width should never be much less where the roof is of double pitch. Single pitched houses should not exceed sixteen feet in width.

Mistakes are frequently made in the erection of structures for the growth of plants which, notwithstanding all the skill and art of experienced gardeners, render it impossible to arrive at satisfactory results. One of the most common of these is the excessive height of the roof. Men of experience in the construction and use of glass houses, have satisfied themselves that the lowest elevation which the uses and purposes of the building will admit, is the best. The difference in temperature between the floor and roof of a house twenty feet in height, will vary from ten to fifteen degrees. It is obviously desirable that there should be as little difference as possible in the temperature of the air on the ground, among the lower parts of the plants, and in the upper regions of the house. The nearer we can approach an equilibrium, the better success will attend our efforts. Nurserymen generally, and sometimes other cultivators, understand this, and they build their plant houses with roofs of low pitch, affording scarcely room to stand upright within them. Their plants are thus brought near the glass, and they grow stocky and firm, presenting quite a different appearance from the attenuated specimens frequently met with in private establishments.

HEATING.

The proper heating of Horticultural buildings being an important feature in their general management, and an essential condition of their success, we shall consider the subject at some length, availing ourselves of the practical experience of others, as well as of the knowledge we have acquired in our own experiments and practice.

Hot air stoves have been so generally condemned and discarded as a means of heating glass structures, that we shall not discuss their faults or merits, but confine ourselves to heating by flues, steam, and hot water in pipes and tanks.

Flues.—Flues have been generally used in heating for many years, and although the method is rude, imperfect and unsatisfactory, they possess certain advantages on the score of economy, which will prevent their total supercedure until some equally cheap and effective method shall be found, to take their place. It cannot be questioned that houses of moderate extent can be heated at much less expense for the original cost of apparatus by the flue system than by any other now before the public. Flues have the advantage over steam or hot water in their power to