The Air of Sewers. 



503 



Miflet (' Biedemann's Centralbl.,' 1880, p. 227) states that air taken 

 from above a sink was rich in micro-organisms. 



In detailing onr own observations it may be as well, in the first 

 place, to give some acconnt of the sewers in which they were made. 

 The main sewer of Westminster Palace,* in which our first observa- 

 tions were made, ran along underneath the open courts in the centre 

 of the building from the neighbourhood of the Victoria Tower to 

 that of the Clock Tower, a short way beyond which it joined the main 

 low-level metropolitan sewer. Along its course it varied irregularly 

 in height from A±\ to 10-|- feet. It was ventilated by suction from the 

 large furnace at the foot of the Clock Tower, and was cut off by a 

 penstock from the metropolitan sewer. The air drawn into the shaft 

 of the furnace almost all came from openings near the Clock Tower 

 end of the sewer. In the rest of the sewer there were no open 

 gratings, and the draught was feeble. On opening the trap-door of 

 a man-hole near the Victoria Tower there was an upward rush of air 

 and condensed vapour, in spite of the very powerful suction at the 

 other end of the sewer. The sewer was flushed daily. It was clean, 

 and the flow of sewage was pretty rapid. The water frequently 

 accumulated in the sewer during rain owing to rise of the level of 

 the water in the metropolitan sewer. Our analyses were made when 

 the water was escaping freely. 



The second set of analyses at Westminster was made after the 

 ventilation of the sewer had been altered by carrying an additional 

 shaft to the furnace and placing inlet gratings in suitable positions. 

 By this means the draught along the sewer from the neighbourhood 

 of the Victoria Tower was much increased. 



We owe the facilities which were afforded us for examining the air 

 in the Dundee sewers to the courtesy of Mr. Mackison, Burgh Engi- 

 neer. We met with a variety of conditions in these sewers. They 

 are all ventilated by open gratings placed in the roadway at distances 

 of about 50 yards apart, and also by the open drain grids placed along 

 each side of the road at distances of about 40 yards. The flow of 

 sewage was in almost every case pretty rapid at the time w T hen our 

 analyses were made. The sewers in Commercial Street, Overgate, 

 and Nethergate are egg-shaped ; that in Murraygate is a large circu- 

 lar sewer. Those in Reform Street and Dock Street had originally 

 been large, old, flat-bottomed stone sewers, but had been partially 

 altered by the substitution of a bottom similar to that of an egg- 

 shaped sewer. The Dock Street sewer is alternately filled and emptied 

 by the tide, as is also the sewer in Commercial Street, opposite Ex- 

 change Street. The approximate heights of the several sewers are 



* This sewer has now (18S7) been replaced by a pipe, on the recommendation of 

 the Select Committee. 



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