The economising of space was effected in two well-marked directions. Houses and shops were erected on old London Bridge, and half-timbered houses with many over-sailing storeys were very largely built in the city. There is an excellent representation of old London Bridge with its closely packed houses in Robert Prycke's bird's-eye view (here produced). It may be well to add a word or two here to explain what is implied by the term half-timbered houses, popular ideas upon the subject being somewhat vague. There are, in fact, several different interpretations as to its significance. One meaning of "half-timber" is trunks of wood split in half; but this is used mainly in connection with shipbuilding. One writer states that half-timber work is so called "because the timbers which show on the face are about the same width as the spaces between." Gwilt describes a half-timber building as "a structure formed of studding, with sills, lintels, struts, and braces, sometimes filled in with brick-work, and plastered over on both sides." Parker defines a half-timber house as having "foundations and the ground floor only of stone, the upper part being of wood." With these different definitions there is no wonder that popular ideas as to what a half-timber house actually is are rather hazy. The point of most importance, however, is not the mere verbal explanation adopted in technical handbooks, but the characteristics of this kind of structure, differentiating it from those built up from the foundations of one species of material, such as stone, or brick, or what-not. The following may be regarded as the essential features of half-timber houses or timber-framed houses (for the terms are practically synonymous): (1) The foundations and the lower parts of the walls, sometimes up to the sills of the ground-floor windows, are of stone or brickwork. Above this the house is a timber structure as far as its main outline and its sustaining parts are concerned, whatever may be the character of the material with which the intervening spaces are filled. (2) In old buildings of this kind each range or floor was made to project somewhat beyond that below it, producing what are technically termed over-sailing storeys. The advantages of this kind of construction were manifold. It gave to rooms on the upper floor or floors greater dimensions than those on the ground floor. It also imparted structural balance, and afforded a convenient opportunity of strengthening the whole structure by means of external brackets. Moreover, each overhanging or over-sailing storey tended to shelter from the weather the storey below it. The principle of over-sailing storeys was entirely due to the use of timber in house construction.