The older parts of London were being rapidly re-built, and open spaces at the rear of buildings were being gradually covered by buildings. Of St. Pancras the Medical Officer of Health wrote (1896):-- "... There is a prospect that in course of time the whole of the open space about buildings may disappear.... Old houses possessing yards, areas, open spaces, in some form at the front or back or both, are being re-built in such a manner as to entirely cover the whole ground area two or three storeys up--leaving not a particle of open space." The restrictions imposed by the Building Acts were of the most illusory character, and as the Acts were mostly future in their operation, and not retrospective, their effect was also limited. Any "owner" was entitled to re-build on "old foundations," no matter how crowded the houses were on the spot, so new buildings were usually only a resurrection in huger and more perpetual and objectionable form of the evils which ought, as far as possible, to have been eradicated. During the year 1894 the London Building Law was consolidated and amended. The Act recognised, for the first time in London, the principle that, in addition to the height of the building being proportionate to the width of the street on which it abuts, the amount of open space about the rear of a building should also be proportionate to its height, and hence the future crowding of buildings on area was put under limitation. But how small was the limitation, how small the concessions exacted from "owners" in this matter, and how miserably late they came in the history of London building operations. The tendency of house construction in London was to ever larger size, to greater height. To how great an extent this had been carried on in the "City" was described by the Medical Officer of Health in 1894:-- "It would be a fair and moderate estimate to put the superficial area (of the City) at _four square miles_ instead of one. We have only to point to the construction of business premises--the piling of one floor over another for many storeys high, each floor being occupied by separate occupiers, forming in itself a distinct tenancy, having all the rights and privileges of an independent building, and claiming as much attention from every branch of our municipal system as if it stood alone.... We have, in fact, to deal with about 28,000 separate tenancies, with a day population of 301,384." In some of the more well-to-do parts of the metropolis great blocks of buildings were built and let out in flats, most of them with the minimum of light and air prescribed by narrow laws. In other districts of London considerable numbers of small houses were removed, and large blocks of artizans' dwellings erected in their stead. Thus, in the parish of St. Luke, nearly one-fifth of the entire population resided in the ten blocks of artizans' dwellings which existed there.