THE FIRST GERMAN MUNICIPAL EXPOSITION 8 1 3
the existing sewers for drainage purposes, building a new system for sewerage. Aachen and Konigsberg are evidently in a transi- tion state, for part of their respective systems is of the old type, and part is of the double-conduit type. The newly built sewer systems consist, not of two sets of pipes, but of single sets of double-pipe sewers. The upper pipe is built large enough to drain the streets readily, even after excessive rainfall. The lower pipe is smaller, serving for sewage, the amount of which is small and not subject to great vari- ation. An example of this type was exhibited by Bromberg.
The material for the great trunk sewers is usually pressed cement or bricks. The other sewers are usually built of pressed cement with a dressing of tile plates along the bottom. This surface is glossy, non-absorbent, and is not sus- ceptible to acids as is the cement. The pressed-cement con- struction is well adapted to the double-pipe system. The exhibit of the manufacturing firms made in this section of the exposition was especially good. It formed an able supplement to the exhibit of the municipalities.
Almost every municipality exhibiting in this section showed its well-developed network of sewers. Schoneberg has a new system a unified circulation system. It has hygienic and tech- nical advantages over the ramified system, in that it does not have the great number of Gipfelpunkten, with their foul exhala- tions, and admits of effective flushing and of circulation of air through the whole network. Halle combines a groundwater drain with her trunk sewer.
2. Accessories. Street drainage is freed of mud and coarse materials before entering the sewers, by means of gullies, as exhibited by Berlin, or by means of removable buckets hung in the gullies, as exhibited by Wiesbaden, Leipzig, and Dresden (cf. illustration 1 ). The former have to be scraped and cleaned; the latter are removed, emptied into wagons, and replaced. In either case the cleaning is thorough and frequent. Where the sludge
'Vol. IX, opposite pp. 626 and 628.
