It is difficult to realize a drought where there are many poplars.  And yet their green is not rich; the coolest have a colour much mingled with a cloud-grey.  It does but need fresh and simple eyes to recognize their unfaded life.  When the other trees grow dark and keep still, the poplar and the aspen do not darken—­or hardly—­and the deepest summer will not find a day in which they do not keep awake.  No waters are so vigilant, even where a lake is bare to the wind.

When Keats said of his Dian that she fastened up her hair “with fingers cool as aspen leaves,” he knew the coolest thing in the world.  It is a coolness of colour, as well as of a leaf which the breeze takes on both sides—­the greenish and the greyish.  The poplar green has no glows, no gold; it is an austere colour, as little rich as the colour of willows, and less silvery than theirs.  The sun can hardly gild it; but he can shine between.  Poplars and aspens let the sun through with the wind.  You may have the sky sprinkled through them in high midsummer, when all the woods are close.

Sending your fancy poplar-gathering, then, you ensnare wild trees, beating with life.  No fisher’s net ever took such glancing fishes, nor did the net of a constellation’s shape ever enclose more vibrating Pleiades.

CLOUD

During a part of the year London does not see the clouds.  Not to see the clear sky might seem her chief loss, but that is shared by the rest of England, and is, besides, but a slight privation.  Not to see the clear sky is, elsewhere, to see the cloud.  But not so in London.  You may go for a week or two at a time, even though you hold your head up as you walk, and even though you have windows that really open, and yet you shall see no cloud, or but a single edge, the fragment of a form.

Guillotine windows never wholly open, but are filled with a doubled glass towards the sky when you open them towards the street.  They are, therefore, a sure sign that for all the years when no other windows were used in London, nobody there cared much for the sky, or even knew so much as whether there were a sky.

But the privation of cloud is indeed a graver loss than the world knows.  Terrestrial scenery is much, but it is not all.  Men go in search of it; but the celestial scenery journeys to them.  It goes its way round the world.  It has no nation, it costs no weariness, it knows no bonds.  The terrestrial scenery—­the tourist’s—­is a prisoner compared with this.  The tourist’s scenery moves indeed, but only like Wordsworth’s maiden, with earth’s diurnal course; it is made as fast as its own graves.  And for its changes it depends upon the mobility of the skies.  The mere green flushing of its own sap makes only the least of its varieties; for the greater it must wait upon the visits of the light.  Spring and autumn are inconsiderable events in a landscape compared with the shadows of a cloud.