12 THE TONER LECTURES. 



I believe, and I think that I am supported in the belief by the 

 opinion of the best sanitarians of the world, that this condition is 

 absolutely indispensable to proper sewerage. Household wastes 

 retained longer than this enter into a decomposition, extremely 

 foul on account of their original character, and made still worse 

 by the conditions under which they are decomposing. It is in the 

 decomposition of such material in soil-pipes and in sewers, alone, 

 that we'are to find the seat of the enemy of which we hear so much 

 under the name of " sewer-gas." This much decried and insidious 

 sewer-gas is probably entitled to most of the blame it receives for 

 its own direct action, and to as much more from the fact that 

 it so often acts as a vehicle for the germs, or causative particles 

 of specific diseases. There is no safety in sewerage or in house- 

 drainage until we prevent the production of these gases, and there 

 are no means of accomplishing this, short of the entire cleanliness 

 of every pipe, drain, and sewer which serves for the removal of foul 

 organic matter. To secure this condition is within the power of 

 the engineer. There may still be a very slight sliming of the walls 

 of the best sewer, and a feeble decomposition of matters so ad- 

 hering will be inevitable ; but its amount is so slight that it is 

 easily within the reach of simple measures of ventilation to prevent 

 it from causing injury or perceptible odor. It is true that there 

 are very few sewers now existing which are in this condition, but 

 it is equally true that the construction of such sewers would be 

 materially cheaper than that of those which are more liable to 

 become ofiensive. 



I think it may be set down as an indisputable proposition, that 

 before the city of Washington can be considered to be as well 

 drained as it should be, every foot of the sewers with which its 

 houses are connected must be so improved as to be at all times 

 entirely free from deposits of organic matter. 



This end is to be secured by the following provisions : (1.) Every 

 sewer should be of such size that its regular flow, except near its 

 upper end, shall be sufficient to carry forward all matters of what- 



