The azure June hardly leaves a trace of the local grey of smoke. All, by some accident of aspect, is a vague blue, although the smoke, seen from the Greenwich heights, leaves nothing unveiled, cancels the horizon, and barely lets the lovely dome of St. Paul's show a dark blue form upon the close background of thick and sunny air. And blue, like the rest, is that one wide road which takes here so majestic a sweep--the river. It is the river of chimneys; they stand, on either bank, as unequal in growth as a group of children; they crowd together, they stand apart, they straggle, but if they have any law, it is the river's. They mark its path as reeds and rushes might do in meadows. The hidden reaches are traced by this black growth, followed and discovered. The chimneys will hardly let the river go, but cling to the track of his waters when the town is dwindling eastwards, and stand conspicuous among the flats when the houses have at last, at last, ceased. Apart from the river they are almost as rare in London as in Naples, and it is not to them we owe the chief part of our 'sky,' but to the steamers, to the trains, and, more than all, to the unnumbered houses. If ever London is to be restored to her own mists--not to great brightness, but to the tender exhalations that are now burlesqued by smoke, to the true climate of nature, the marshes, and the north, it will obviously be the work of laws touching the houses rather than the factories. The river is perpetually overhung, involved, tangled, in that indefinite and unshapely cloud. It looks blue from the Greenwich hill, but not blue with the blue of pure sunny waters; it is blue because blue is the trick of this midsummer light seen from this one point. The blue road lies open and flat, from the dazzling confusion of the west, whence it comes, to the dimmer confusion of the north, whither the great curve tends. It is a road more level than the tyrannously level rails, but there is no haste in it. The unceasing motion of the tidal Thames seems to make it wait about the bridges of London. The accustomed versifier himself will hardly bid it flow on, so often is it seen to flow back. Because it is so constantly chidden and driven by the sea, the long tendency, brought from its first source and kept between so many fields and over all the noisy weirs, is concealed. That flowing lurks still, but you cannot find it among the rhythmic tides. It is not expressed, and there is no sense of the final sea in the coming and going of these turbid waters. The unceasing seaward flow is their secret.