THE CLEANING OF PAVEMENTS 



Owing to the fact that street dirt is composed of 

 variable ingredients mixed in variable proportions, no 

 analysis or series of analyses is capable of chemiciod 

 exactly indicating its composition. It is too JJJ;,"^"" 

 indefinite a substance to be definitely described. Street Dirt 



Little is known about the nature of the bacteria 

 present in street dirt, although tests show they are 

 numerous. Most of the bacteria are probably of 

 harmless, saprophytic species. The germs of disease 

 probably do not live long, and rarely, if ever, multiply 

 in street dirt. The predominating kinds are, we may 

 safely conclude, those which are concerned in the 

 processes of decay. 



To dispose of the dirt which soils the streets, two 

 general methods exist. Innumerable as are the sources, 

 there are but two avenues of escape. It , 



r Methods of 



must be picked up and hauled away in carts street ciean- 



.1 inK 



or it must flow with water into the sewers. 



Usually a good deal of street dirt flows away by the 

 sewers during rain-storms, but this method of disposing 

 of it should limit the dirt to finely divided matter. In 

 some cities, notably Paris, the sewers have been built 

 with the idea of carrying off all the street dirt that can 

 reasonably be emptied into them, but there is generally 

 objection to this practice. The best engineering opinion 

 is that a city's sewers can, and should, be made to carry 

 a good deal of fine dirt from the streets. The large, 

 bulky, heavy particles must be removed otherwise. 



It cannot be too often emphasized that good pave- 

 ments in good repair are indispensible to good work in 

 street cleaning. It makes less difference what 



Pavements 



kind of pavement is employed than what con- 

 dition the pavement is in. Every sort of pavement 



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