Blithewood, formerly the seat of R. Donaldson, Esq., (now John Bard, Esq.), near Barrytown, on the Hudson, is one of the most charming villa residences in the Union. The natural scenery here, is nowhere surpassed in its enchanting union of softness and dignity - the river being four miles wide, its placid bosom broken only by islands and gleaming sails, and the horizon grandly closing in with the tall blue summits of the distant Kaatskills. The smiling, gently varied lawn is studded with groups and masses of fine forest and ornamental trees, beneath which are walks leading in easy curves to rustic seats, and summer houses placed in secluded spots, or to openings affording most lovely prospects. In various situations near the house and upon the lawn, sculptured vases of Maltese stone are also disposed in such a manner as to give a refined and classic air to the grounds.

As a pendant to this graceful landscape, there is within the grounds scenery of an opposite character, equally wild and picturesque - a fine, bold stream, fringed with woody banks, and dashing over several rocky cascades, thirty or forty feet in height, and falling altogether a hundred feet in a distance of half a mile. There are also, within the grounds, a pretty gardener's lodge, in the rural cottage style, and a new entrance lodge by the gate, in the bracketed mode; in short, we can recall no place of moderate extent, where nature and tasteful art are both so harmoniously combined to express grace and elegance.

Montgomery Place, the residence of Mrs. Edward Livingston, which is also situated on the Hudson, near Barry-town, deserves a more extended notice than our present limits allow, for it is, as a whole, nowhere surpassed in America, in point of location, natural beauty, or the landscape gardening charms which it exhibits.

It is one of our oldest improved country seats, having been originally the residence of Gen. Montgomery, the hero of Quebec. On the death of his widow it passed into the hands of her brother, Edward Livingston, Esq., the late minister to France, and up to the present moment has always received the most tasteful and judicious treatment.

The lover of the expressive in nature, or the beautiful in art, will find here innumerable subjects for this study. The natural scenery in many portions approaches the character of grandeur, and the foreground of rich woods and lawns, stretching out on all sides of the mountain, completes a home landscape of dignified and elegant seclusion, rarely surpassed in any country.

Among the fine features of this estate are the "Wilderness," a richly wooded and highly picturesque valley, filled with the richest growth of trees, and threaded with dark, intricate, and mazy walks, along which are placed a variety of rustic seats. This valley is musical with the sound of waterfalls, of which there are several fine ones in the bold impetuous stream which finds its course through the lower part of the wilderness. Near the further end of the valley is a beautiful lake, half of which lies cool and dark under the shadow of tall trees, while the other half gleams in the open sunlight.

In a part of the lawn, near the house, yet so surrounded by a dark setting of trees and shrubs as to form a rich picture by itself, is one of the most perfect flower gardens in the country, laid out in the arabesque manner, and glowing with masses of the gayest colors - each bed being composed wholly of a single hue. A large conservatory, an exotic garden, an arboretum, etc., are among the features of interest in this admirable residence. Including a drive through a fine bit of natural wood, south of the mansion, there are five miles of highly varied and picturesque private roads and walks, through the pleasure-grounds of Montgomery Place.

Ellerslie is the seat of William Kelly, Esq.* It is three miles below Rhinebeck. It comprises over six hundred acres, and is one of our finest examples of high keeping and good management, both in an ornamental and an agricultural point of view. The house is conspicuously placed on a commanding natural terrace, with a fair foreground of park surface below it, studded with beautiful groups of elms and oaks, and a very fine reach of river and distant hills. This is one of the most celebrated places on the Hudson, and there are few that so well pay the lover of improved landscape for a visit.

Just below Ellerslie are the fine mansion and pleasing grounds of Wm. Emmet, Esq., - the former a stone edifice, in the castellated style, and the latter forming a most agreeable point on the margin of the river.

The seat of Mrs. Gardiner Howland, near New Hamburgh, is not only beautiful in situation, but is laid out with great care, and is especially remarkable for the many rare trees and shrubs collected in its grounds.

Wodenethe, near Fishkill landing, is the seat of H. W. Sargent, Esq., and is a bijou full of interest for the lover of rural beauty; abounding in rare trees, shrubs, and plants, as well as vases, and objects of rural embellishment of all kinds.

Kenwood, formerly the residence of J. Rathbone, Esq., is one mile south of Albany. Ten years ago this spot was a wild and densely wooded hill, almost inaccessible. With great taste and industry Mr. Rathbone has converted it into a country residence of much picturesque beauty, erected in the Tudor style, one of the best villas in the country, with a gate-lodge in the same mode, and laid out the grounds with remarkable skill and good taste. There are about 1200 acres in this estate, and pleasure grounds, forcing houses, and gardens, are now flourishing where all was so lately in the rudest state of nature; while, by the judicious preservation of natural wood, the effect of a long cultivated demesne has been given to the whole.

* More recently the home of the late Levi P. Morton.