Another consequence of the old compression within narrow walls was that, as population increased, the houses grew more lofty. How high the Romans built, or were allowed to build, in republican times we cannot tell. The tendency was certainly to build higher and higher, and sky-scrapers would perhaps have become the rule if the ancient Roman had understood the use of materials both sufficiently light and sufficiently strong, or if he had been forced to establish his work on secure foundations. In point of fact there had been, and there continued to be, too much of jerry-building. Houses sometimes collapsed, and many were unsubstantially shored up. A flood or an earthquake was apt to find them out, and there was frequent peril in the streets. The majority of the abodes of people of humble means were not like those in smaller towns, such as Pompeii, still less like those in the country. They were "tenement houses," large blocks let out in rooms and flats, and it was natural that landlords should make haste to run them up and to increase the number of their stories. When Augustus became emperor he enacted what may be called a Metropolitan Building Act, which insisted on firmer foundations and limited the height to 70 feet. That act was apparently still in force in the age of Nero, and we may take it that along the more frequented streets the houses commonly ran to a height of four or five stories. They looked the taller because of the narrowness of the street itself. While it is perhaps, though not necessarily, an exaggeration for the epigrammatist--who lived "up three pair of stairs, and high ones"--to say that he could touch his opposite neighbour with his hand, it is at least an indication of the truth. Some of the narrower lanes between blocks cannot have been more than a few feet across. Nor does it appear that the occupants' of rooms opening on the streets were very particular as to what they threw out in the way of rubbish or dirty water. It is true that there were aediles, or officers to look after the order of the streets and public places, but their efforts seem to have been mainly directed to preventing conspicuous obstruction. Practices which we should regard as heinous were treated lightly or disregarded. To make matters worse, the shopkeepers, who occupied the lower fronts of most of such houses, took the greatest liberties in encroaching upon the roadway when exhibiting their wares, and it was not till twenty years later than our date that the Emperor Domitian ordered them to keep within their own thresholds.