A species of useful decoration, which is perhaps more naturally suggested than any other, is the bridge. Where a constant stream, of greater or less size, runs through the grounds, and divides the banks on opposite sides, a bridge of some description, if it is only a narrow plank over a rivulet, is highly necessary. In pieces of artificial water that are irregular in outline, a narrow strait is often purposely made, with the view of introducing a bridge for effect.

When the stream is large and bold, a handsome architectural bridge of stone or timber is by far the most suitable; especially if the stream is near the house, or if it is crossed on the approach road to the mansion; because a character of permanence and solidity is requisite in such cases. But when it is only a winding rivulet or crystal brook, which meanders along beneath the shadow of tufts of clustering foliage of the pleasure ground or park, a rustic bridge may be brought in with the happiest effect.

Rockwork is another kind of decoration sometimes introduced in particular portions of the scenery of a residence. When well executed, that is, so as to have a natural and harmonious expression, the effect is highly pleasing. We have seen, however, in places where a high keeping and good taste otherwise prevailed, such a barbarous melange, or confused pile of stones mingled with soil, and planted over with dwarfish plants dignified with the name of rock-work, that we have been led to believe that it is much better to attempt nothing of the kind, unless there is a suitable place for its display, and at the same time, the person attempting it is sufficiently an artist, imbued with the spirit of nature in her various compositions and combinations, to be able to produce something higher than a caricature of her works.

The object of rockwork is to produce in scenery or portions of a scene, naturally in a great measure destitute of groups of rocks and their accompanying drapery of plants and foliage, something of the picturesque effect which such natural assemblages confer. To succeed in this, it is evident that we must not heap up little hillocks of mould and smooth stones, in the midst of an open lawn, or the center of a flower-garden. But if we can make choice of a situation where a rocky bank or knoll already partially exists, or would be in keeping with the form of the ground and the character of the scene, then we may introduce such accompaniments with the best possible hope of success.

It often happens in a place of considerable extent, that somewehere in conducting the walks through the grounds, we meet with a ridge with a small rocky face, or perhaps with a large rugged single rock, or a bank where rocky summits just protrude themselves through the surface. The common feeling against such uncouth objects, would direct them to be cleared away at once out of sight. But let us take the case of the large rugged rock, and commence our picturesque operations upon it. We will begin by collecting from some rocky hill or valley in the neighborhood of the estate, a sufficient quantity of rugged rocks, in size from a few pounds to half a ton or more, if necessary, preferring always such as are already coated with mosses and lichens. These we will assemble around the base of a large rock, in an irregular somewhat pyramidal group, bedding them sometimes partially, sometimes almost entirely in soil heaped in irregular piles around the rock. The rocks must be arranged in a natural manner, avoiding all regularity and appearance of formal art, but placing them sometimes in groups of half a dozen together, overhanging each other, and sometimes half bedded in the soil, and a little distance apart. There are no rules to be given for such operations, but the study of natural groups, of a character similar to that which we wish to produce, will afford sufficient hints if the artist is "Prodigue de genie,"* and has a perception of the natural beauty which he desires to imitate.

The rockwork once formed, choice trailing, creeping, and alpine plants, such as delight naturally in similar situations, may be planted in the soil which fills the interstices between the rocks: when these grow to fill their proper places, partly concealing and adorning the rocks with their neat green foliage and pretty blossoms, the effect of the whole, if properly done, will be like some exquisite portion of a rocky bank in wild scenery, and will be found to give an air at once striking and picturesque to the little scene where it is situated.

In small places where the grounds are extremely limited, and the owner wishes to form a rockwork for the growth of alpine and other similar plants, if there are no natural indications of a rocky surface, a rockwork may sometimes be introduced without violating good taste by preparing natural indications artificially, if we may use such a term.

* A favorite quotation of Mr. Downing's; see page 76.

If a few of the rocks to be employed in the rockwork are sunk half or three-fourths their depth in the soil near the site of the proposed rockwork, so as to have the appearance of a rocky ridge just cropping out, as the geologists say, then the rockwork will, to the eye of a spectator, seem to be connected with, and growing out of this rocky spur or ridge below: or, in other words, there will be an obvious reason for its being situated there, instead of its presenting a wholly artificial appearance.

In a previous page, when treating of the banks of pieces of water formed by art, we endeavored to show how the natural appearance of such banks would be improved by the judicious introduction of rocks partially imbedded into and holding them up. Such situations, in the case of a small lake or pond, or a brook, are admirable sites for rockwork. Where the materials of a suitable kind are abundant, and tasteful ingenuity is not wanting, surprising effects may be produced in a small space. Caves and grottoes, where ferns and mosses would thrive admirably with the gentle drip from the roof, might be made of the overarching rocks arranged so as to appear like small natural caverns. Let the exterior be partially planted with low shrubs and climbing plants, as the wild clematis, and the effect of such bits of landscape could not but be agreeable in secluded portions of the grounds.