556 [AsSEMBLTr 



ameter, so increased the velocity of the stream, that there was nc 

 increase of its sectional area. 



It has been observed that a three inch pipe serving as the main 

 outfall for the drainage of an area of ten acres of land was never 

 more than half filled, indicating the expediency of making land 

 drainage pipes still smaller, improving their manufacture, and 

 making them more exact in form, and laying them more accu- 

 rately. 



The annual rain that falls is about forty per cent, and only 

 twenty-five per cent of that whicli falls from October to March 

 passes back to the atmosphere by evaporation, but from April to^ 

 September, inclusive, ninety-two per cent is evaporated. In Au- 

 gust the soil is in its driest state, but still filtration takes place. 

 If all the water derived from rain during the six colder months 

 oi the year were allowed to accumulate in the soil, such land 

 would be perfectly w^et, and require the whole of that period, by 

 the unaided force of evaporation, to keep it in a uniform moist con- 

 dition, while deep-covered drains would relieve the same soils of 

 excess of moisture in a few hours after every shower, even in the 

 rainy stason. The excess of rain water to be disposed of during the 

 six coldest months by some other process than evaporation amounts 

 to no less a weight than one thousand and fifty tons per acre. Parts 

 ((four city are badly drained, and the streets become receptacles for 

 refuse and cxcrementitious matters, which tend much to increase 

 the mortality; in iact, the average age of our inhabitants does not 

 exceed twenty-one years. In 1844 more than 33,000 of our po- 

 pulation lived in badly drained courts and alleys, and nearly 

 seven tlnnisand in cellars. In these dark, damp, chilly places^ 

 fevers and other contagious and inflammatory diseases prevailed. 

 In Philadelphia half of those born die before the fifth year, and 

 twenty-seven per cent before the forty-sixth year. In Bethnal 

 Green, one of the worst districts in London, it is forty-nine years, 

 and the average in London is fifty-three years. Absence of drains 

 and deficient sewerage tend to increase the mortality of cities by 

 contaminating the air which its inhabitants are compelled to 

 breathe. The calculation is that each individual requires a daily 

 supply of more than six hundred cubic feet of pure air to main- 



