The principle on which single trees and shrubs, and small groups of these, are planted, is precisely the same as that by which groups are disposed on lawn, viz. the production of a whole, by heightening the effect of the parts which compose that whole. This principle will give the following rules: - First rule: As no single object can form a whole, because the idea of a whole supposes parts which compose it, a single tree, that is, a tree standing completely detached from every other tree, and every other object which rises above the surface, should seldom or never be planted in landscapes where picturesque beauty is an object. A single tree, Mr. Price has observed, is scarcely to be found in nature. In our native woods and forests there is hardly such a thing to be met with as a tree not connected with another tree, or bush, or rock; and, in the landscapes of eminent painters, a tree apart from other trees is, almost without an exception, connected or grouped with buildings or animals. Second rule: As the idea of a whole includes in it, at least, the idea of commencement, progress, and conclusion; or beginning, middle, and end; so the smallest number of trees, or rather of objects, which compose a whole are three. Third rule: As the idea of a whole includes the idea of greater and smaller, no three trees or shrubs, or other objects, should be planted or placed together exactly of the same size, or at regular distances from one another. Fourth rule: As the object of small groups is to heighten effect, they ought never to be planted but with reference to the masses of woods or plantations already existing, the inequalities of the ground's surface, or the situation of buildings, rocks, or water. Fifth rule: Small groups ought to be more frequently planted in front of projecting masses of plantation than in bays and recesses, and more frequently on knolls, or raised parts of the surface, than in hollows. Sixth rule: No small group ought to be so planted as that it might afterwards be moved to the right or left, backwards or forwards, without injuring the scene to which it belongs. Seventh rule: No small group ought ever to be placed in the precise Huddle of any scene, unless it be avowedly artificial, or the intention be to diminish its apparent size, or destroy breadth of effect. Eight rule: All masses of wood in park scenery, or wherever it is intended to imitate nature in planting, should be composed of aggregations of groups. Ninth rule: Where there are roads, fences, buildings, or watercourses, groups should generally be placed near them, rather than towards the middle of the park or lawn. Tenth rule: In situations of the kind last mentioned, one or two trees are often admissible, as forming a whole with the other objects. Eleventh rule: A tree, with a shrub or a creeper planted in the same hole, will form a better group than two trees planted in the same hole. We could add to the number of these rules; but we think we have done enough to show the difficulty of the subject, and to prove how thoroughly almost every park and lawn in the country is deformed by the system of dotting, as it is called, at present so generally practised. We were surprised at the extent to which this system has been carried at Alton Towers, Trentham, Chatsworth, Heaton Park, and other places, where we expected better things. Other faults common to the grounds of most residences, but most conspicuous and offensive in those of small villas, are the depth, nakedness, and spade-marks of the edges to the walks and roads. Many gardeners are not aware that this is a great fault, or we should not find it prevailing in places otherwise respectably kept. It is a fault, because the lines so produced are too harsh and conspicuous, and attract too much attention in the general view. There can be no absolute depth assigned for the edge of a walk, any more than there can be for its breadth: relative circumstances must determine both. Nevertheless, we may lay it down as a rule, that a walk 6 ft. broad, through a smooth lawn, should never have the edges deeper than 1 in.; a 12 ft. walk or road may have an edge 2 in. deep, but not more. The edges, whether of 1 in. or 2 in., should always present a surface of grass, and not of raw earth, as left by the spade. Natural walks, with broken edges, should be rather above the level of the adjoining surface, in order to throw off the water. The fault we have just mentioned every possessor of a villa may detect for himself; and we may safely appeal to his own feelings, whether adhering to the depth mentioned would not be a great improvement to the appearance of garden scenery. Other faults in the walks and grounds of villa residences we shall leave for the present, and proceed next to notice some in their architecture and disposition on the ground. Though we are not a professional architect, yet we pretend to as thorough a knowledge of the principles of architecture, as of those of landscape-gardening; and, though the architects who design buildings to our taste are not quite so few as the gardeners who lay out grounds to please us, yet by far the greater number of them are as completely without the painter's eye as are the generality of gardeners. The greater number of even the best architects are the slaves of rules drawn from precedents instead of from principles; and this, indeed, is the great bar to improvement in almost every thing. The fundamental principles of architecture are of two kinds, because its objects are two, viz. use and beauty: fitness, strength, and durability compose the first of these principles; the idea of an expressive whole, the second; and in an extended sense of the word, this principle will include the other. A whole in architecture, as in landscape-gardening, may be regularly symmetrical, or irregularly symmetrical. In the one case, as in the other, the test of success is the production of a whole expressive of the purpose for which it is intended. We shall not here, however, dilate on first principles, but rather proceed at once to the details of our objections.