whole space occupied by the buildings. So then the buildings are to be cleared away to convert the whole city into a garden? Not so, only the roofs of the buildings.
In southern climates buildings are constructed with flat roofs, as there is no snow, and comparatively little rain. In some cases the roof consists of a floor of canes or sticks, covered with mud mixed with chopped straw. In South America, La Plata, where mist and heavy rain fall at times, flat roofs are constructed by laying first parallel stems of palm-trees from wall to wall, filling the crevices with sticks and mud, laying thereon flat tiles cemented with a mixture of lime, burnt brick dust, and blood; covering the joints with a second layer of tiles, and then again with a third layer. This is impervious to water; and as there are no heavy carts or waggons to induce vibration, this kind of roof does not crack. Roofs depart further from the horizontal and grow more vertical as we go north; and in Canada they get to a steeple form, like that of Westminster Abbey’s mountain ridge. Almost too steep for tiling, they use small oblong boards, called shingles, nailed on to them, or they are covered with tin plates, which glisten like eastern minarets in the sunshine. On such roofs snow cannot lie; three inches thickness of snow slides off in a kind of small avalanche, to the annoyance of the passers by.
Steep roofs are necessarily lofty, and are much exposed to damage by wind; and what are called Italian roofs, of much less fall, are therefore largely used; but the steep roofs are truncated in various ways — the apex is sometimes cut off flat, or the height is lessened by making the roof in a series of ridges of the same pitch, with valleys between them and around them, involving risk of the very snow they are pitched to avoid, by the overflowing of the gutters, which are a receptacle of the ashes that pass up the chimneys. Smoke nuisance thus helps to increase rain nuisance. Italian roofs, with external gutters, are not exposed to this; but they involve the difficulty, that if a slate gets loose, the trampling of those who have to repair it breaks many other slates, and at a risk of the repairer falling off the house.
To get access to ordinary roofs for the purpose of repairs, there is usually a trap-door in the attic ceiling, where a ladder is placed on occasion. In the roof itself is another trap-door or a dormer, leading out into a gutter so narrow that one cannot walk along it without disturbing the tiles or slates. Apart from the dirt and overflowing of the gutters, these roofs are rarely in order; and the space below the tiles, called the “cockloft” — probably from having been a roosting place for the fowls in the buildings forming the type of the present structures — is a receptacle for soot, dust, filth, and all the bad air in the house ascending from below: add to this, it is usually all in darkness. Few persons know what this really is, till in case of fire, when they know not how to escape, and risk their lives in slipping from steep gutters on their way to a neighbouring house. Those who have ascended the dark wooden gallery in passing through the dome of St. Paul’s, may have an idea of it, save that they ascend staircases instead of ladders. Thus a space equal to nearly the whole basement area of all the buildings in London is devoted to filth and risk of life, and au incalculable amount of waste in repairs.
This great nuisance has not passed by unnoticed. The space alone — equal to another floor in a house — is wasted, and this space — supposing the air to be free from smoke — is the purest in the whole house, being farthest removed from the surface of the earth. Attempts have been made to construct flat roofs, but rarely successfully. An architect once showed me his own dwelling, over a part of which he had a flat roof, which he boasted was successful. But in every corner there was a stain, and at last he was obliged to own that the cement would crack from time to time, and required constant attention.
The reason is plain. All flat roofs hitherto constructed have been of brittle material, and brittle material— such as water-cement — cracks from subsidence of the ground; from unequal settlement, from expansion and contraction by heat and cold, and from many other causes.
To guard against this, flat roofs are commonly covered with sheet-lead. But this again is a nuisance. To prevent the lead from cracking by the heat and cold, it is laid in broad stripes, the edges being turned over projecting rolls of timber, sufficiently elevated to prevent rain-water from overflowing. We find every alternate ridge is a table-elevation, or a valloy, then a succession of valleys. Such a roof is a nuisance to walk on, independently of the temptation to thieves to steal the lead.
Is it then impossible to make flat and permanent roofs — roofs permanent as a foot-pavement? I think — nay, I’m sure, it is not a difficult operation if set about with common sense. We have for ages made flat roofs to ships at sea — I mean the decks. Planks nailed down side by side are caulked with tarred or pitched hemp. The planks are wet naturally in some climates and artificially in others, and their constant swelling keeps the joints tight. We put wine and liquors into barrels — the wine swells the staves and the liquor does not run out. We put wine and liquors into stone bottles, and we joint the opening with an elastic cork — the cork swells and the liquor does not run out. The difference between these arrangements and that of the flat roofs that let in water is, that in the one case, the materials are elastic, in the others, brittle.
For many years past a valuable building material has been in use; slate sawn or cut into large tables of any required size, from half an inch to three or four inches in thickness. If we suppose four walls to be built up in a square and overlaid with a solid table of this slate, projecting a foot beyond the walls, and with a descending edge to prevent water running underneath to the walls, it is evident that nothing short of a Swiss flood descending the Rhine, and rising upwards, could get access by way of the roof.
But we can’t get slates so large! No! But we can get very large slates, and we can put them together so as to be water-tight.
How?
As we joint, wine-bottles with corks; cork the