The census of 1851 recorded half of the population of Britain as living in towns—the first society in human history to do so. Over the (1) 70 years, the population of Britain had risen at an unprecedented (2) , passing the levels reached in earlier period of (3) when the population had been decimated by epidemics such as the Black Death. But was there any reason for (4) The towns offered a better chance of work and (5) wages than the countryside, (6) many families were trapped in dire poverty and seasonal employment. On the other hand, the countryside was (7) . A baby born in a large town with a population of more than 100,000 in the 1820s might (8) to live to 35; in the 1830s, life expectancy was down to a (9) 29. A comparison between a desperately unhealthy large town and a small market town (10) the costs of migrating in search of work and prosperity. In 1851, a boy born in inner Liverpool had a life expectancy of only 26 years, (11) a boy born in the small market town of Okehampton, (12) could expect to live to 57. Large towns were, (13) , desperately unhealthy, with death from sickness (14) a level not seen since the Black Death. New epidemics were (15) the cities: cholera and typhoid were (16) by polluted water; typhus was spread by lice; and "summer diarrhea" was caused by (17) of flies feeding on horse manure and human (18) The problem was easy to (19) and difficult to solve: too little was invested in the urban environment, (20) sewers, street paving and cleansing, and in pure water and decent housing.