FOUNDATIONS OF LONDON.

King Country Chronicle, Volume VII, Issue 566, 10 May 1913, Page 3

FOUNDATIONS OF LONDON.

TUBES AND BUILDINGS. London is not built upon rock or in a quarry like Paris. North and south of the river there is a more or less elastic superstratum of varying thickness, and below everything a depth of several hundred feet of grey "London clay." Springs and land drainage abound in the gravel, loarr, and silt which constitute the upper crust, and though the clay below as a whole, or in any bulk is impervious to water, it is damp and compressible. It is evi dent that the site of this metropolis was not selected on account of its suitability a i a permanent or satisfactory basis for architectural monuments.

London has become itself by virtue of the river, the city deriving its political and commercial influence from this source as well as its, on the whole, tolerable climate from the once water-washed gravel which overlays the original river edging of silt and from the fresh springs which filter up and through the golden soil. But with these virtues, as in other things, there are drawbacks, and principally that of the generally vicious one of an uncertain foundation.

Inspired sagacity planted the Abbey of St. Peter at Westminister on the one spot amid the marshes of Thorney Island which could carry a great building ; the Cathedral of St. Paul was fixed with relative security upon the isolated hill between the Wall-brook and the Fleet; while the Tower probably occupies the earliest dry spot of a British fort and of the Roman castrum. LONDON ON ITS MARSH. Betwixt these islands of foothold the country was mainly marsh, and though now protected superficially by countless poofs and square miles of pavement it is still fundamentally unregenerate marshland. Venice abides the wonder among cities of the sea. Rotterdam relies i>pon a piledriven security; and London rests upon its soft and speckled bed of marshy gravel and clay. But, in spite of its bad beginnings, architectural glory has come to London, as it does to every city possessing a millennium of continuous usefulness. The past as well as the present of the city is embodied in buildings the stability of which seems, until we are rudely awakened, as essential to it as that of the Constitution to the Realm. We feel instinctively that its monuments must be preserved at all costs, and should disaster overtake one, aB with the Campanile of St. Mark, civic and national sentiment will instantly demand its reereetion just as it was before the fall. The Tower, the Monument, St. Paul's, Bow Church among others, Somerset House, the Templarß Church, Nelson's Column (alas! for its ungainliness), the Whitehall Palace fragment, Westminster Abbey and the Palace there, ancient as to its Hall and modern as , to its Houses of Legislature, St James', and many other monuments are admittedly indispensable to Lon- ' don, no Philistines of art or Babylonians of commerce gainsaying.

Against damage by tooth of Time or by tongue of Fire we are jealously watchful both by repair and hydrant. It is against undue artificial gradual interference with the peculiar conditions of the subsoil that Londoners need nowadays to be on guard. If We were founded on a rock like Jerusalem, like that Holy City we could have neither low-levels sewers nor anderground railways, but the facility with which tubes for sewers and passenger trains are driven through the underlying clay of London presents an actual danger to great buildings which needs most jealous precautionary warning and attention.

THE CONDITIONS OF SAFETY.

The general conditions necessary to the safety of superstructures would seem to include the following, among others: a definite relation between the position of the lines standardised by the Central London Railway and the buildings above ground—there is probably a distance underground at which the substitution of solidly constructed tube ceases to affect the buildings overhead, and this should be exactly ascertained: the special condition of t.ie subsoil of the building; and the weight and shape of the building itself which necessarily are related to this distance of a tube below ground. If the soil is partly loose and the building great and heavy it will be clear that the tube should be relatively at a greater distance below ground to cease to have effect upon the stability of its surface burden. Other conditiuns which suggest themselves are the presence of water in or under the surface strata, and the permanence of its general condition as liable to alteration from surrounding drainage. Distant conditions also may affect remote sites. For instance, it appears to be certain that the Embankment of the Thames from Blackfriars upwards has increased the scour of the river downwards, and that opposite to and under the site of St. Paul's the banka of the river, which is strongly tidal, may have been altered in condition below the water line. Intermittent vibration caused by heavy trainß in a metal tube railway is another factor to be scientifically tested and settled, as the height of a building besides its weight is an important factor. A minute vibration at the base of a building 50ft high that may be disregarded in practice would be ruinous to a rigid tower 500 ft in height. The plan and architectural structure of buildings also cannot be overlooked, as great weight poised upon piers and arches is in more delicate conditions of structural balance than that of a soild four-square tower. Westminster Abbey is more ticklish than Big Ben's campanile, and St. Paul's than the Tower.

The horizontal distance apart of tubes underground, their wilder stations, atid their relation to the position of deep sewers are necessarily factors in the case; the aggregate dis-

turbance of normal conditions by tubes or excavations in a given acreage often may become serious where the separate disturbance causad by one tube, may bs insignificant. NEED OF AN INQUIRY.

Careful public inquiry before a judicial tribunal strengthened by professional assessors should afford opportunity for threshing out the risks connected with underground excavations and railways near to important public buildings, proceedings in which the expenses should be beforehand guaranteed either by the promoters or by public fund?. Experience is accumulating now as to the effect of tubes, both in vibration and construction, but the overmastering interest of the subject to the engineer needs ample balance by the pre-eminent public interest of the preservation of irreplacable monuments, and no risks should be taken. St. Paul's Cathedral is inevitably before the nation's mind now that it is proposed in the interests of tramway communication to create a shallow subterranean way near to the building. It would seem that nearly all the risks possible are to be encoun tered and undertaken in this scheme. It is essential that the structural integrity of the building, which has notoriously suffered since its erection, should be inquired into; that the j history and present condition of the surrounding sites down to the river bed should be examined and tested that the vibration and quantity of the proposed traffic should be ascertained and its effect on lofty buildings determined by experimental analogy and, finally, the ultimate benefit of the whole proposal should be freshly and fairly reviewed before public opinion can be reassured as to this really dangerous attack upon the security of England's greatest architectural monument. —Arthur Beresford Pite, F.R.1.8.A.