PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 583 



special regard for public 'welfare, and which, to. this day, rebuke the mis- 

 taken parsimony of ages and lands which arrogate to themselves specious 

 pretensions of social rank. Farts of buried cities on the shores of the M li- 

 terranean, brought to light after ages of seclusion, ])ut to shame, in their 

 sanitary appliance, the costliest mansions of our proudest modern towns. 



In the scliool of hydraulic engineering it is understood that any proper 

 arrangement of water supply involves an equally complete system of sew- 

 erage. The latter generally follows the former, though it should properly 

 precede it. But cities like those of modern times, rapid in growth and uhcer- 

 tain in local development, arc rarely built up with proper regard to civic 

 necessities, and only adopt plans of public works when forced into it by press- 

 ing sanitary conditions of existence and progress. The ancients were wiser 

 than the men of this generation in these respects, and did not leave their 

 prospective cities without careful provision for necessities which may be 

 better provided for in advance of their occurrence. 



The accumulations of a city which require adequate disposal may be 

 classified as street dirt, house sewage and rain-fall. 



Street dirt, so far as it is made up of garbage, ashes, and other matters 

 of a perishable or solid character, which can be conveniently carted, should 

 not enter the sewers; and the horse roanure and street wash, which rapidly 

 accumulato on the pavements, may or may not be carried into the sewers, 

 as the character of the pavement itself, and the method of carriage, will 

 properly determine. The quantity of manure dropped in the streets of a« 

 large city is much greater than is generally supposed. A London report 

 of 1850, on this point, says: 



" It is considered that the horse dung which falls in the streets of the 

 metropolis, cannot be less than 200,000 tons a year. Much of this, under 

 ordinary circumstances, dries and is pulverized, and with the common soil 

 is carried into houses as dust, and soils clothes and furniture. The odor 

 arising from the surface evaporation of streets when thej' are wet is chiefly 

 from horse dung. Tlie surface water discharged into sewers from the 

 streets and roofs of houses is found to contain as much filth as the soil 

 water from house drains." 



With close laid block pavement, which admits the use of a water jet for 

 sti^ct cleansing (which experience has proved to be much more economical 

 than the street sweeper and dirt cart), this part of the street dirt may 

 properly be washed into the sewers; but the ordinary cobble stone pave- 

 ment will not permit a strong, scouring jet, without risk to its bed, and 

 where in use, indicates the need of dirt carts for all kinds of street dirt, 

 with tiicir attendant imperfections, annoyances and expenses. Among 

 other benefits of the trap block pavement, now being extended through 

 New York, will be its superior cleanliness, when subjected, as it should 

 I be, to the periodical water jet, of adequate power. 



House sewage, discharged from the various household appurtenances,* 

 in a liquid, semi-liquid, and solid state, requires underground disposal. 

 Investigation has shown the singular fact, in our own cities as in Europe, 

 that water supply, for daily consumption, forms a very correct measure of 

 daily sewage flow, and any attention to t'.io quantity of water waste in 

 daily household experience readily explains this connection. The amount 



