Polytechnic Association. 659 



tions are in the right direction, and if persevered in will lead to 

 important imforrnation. 



I will now call your attention, for a few moments, to some practi- 

 cal observations that have been made. "We have heard of many 

 instances where persons who have been engaged removing obstruc- 

 tions from the sewers being suffocated, but I will only refer to the 

 one reported in the Medical Times of London, which took place on 

 February 8th, 1861, where four workmen were killed. These work- 

 men entered one of the branches of the Fleet-street sewer, for the 

 purpose of removing the slime and sand that had collected in the 

 bottom of it. It was soon found that something was wrong with 

 them, and it was afterwards discovered that they had been suffocated 

 by the poisonous gas of the sewer. 



Thorwirth, who has given this subject great attention, and has 

 traversed the interior of the sewers for miles, says that through 

 their whole course millions of bubbles filled with noxious gas are 

 continually rising to the surface of the sewage, the contents of which 

 mingle with the contiguous atmosphere. The same author says that 

 a house will employ an expensive water supply to remove the small 

 amount of filth belonging to itself, in exchange for which it places 

 itself in a position to receive the poisonous gas from all the cloaca of 

 an entire city district. 



Behrend informs us that sewers in Berlin, that are plentifully sup- 

 plied with water, emit an intolerable stench. 



Dr. Thormahlen writes, in regard to the Hamburg sewers, which 

 are well constructed and plentifully supplied with water, that in warm 

 weather a most offensive gas escapes from the sewer inlets, and that 

 by high tides this gas is driven through the house pipes into the 

 dwellings. 



I am enabled to state, from my own observations, that in the city 

 of Cassel the escape of gas from the sewers is very great, and that 

 this escape actually takes place, to the greatest extent, in the higher 

 parts of the city. It is also an established fact, that typhus fevers 

 are much more prevalent in these more elevated parts of that city. 



Mr. Child informs us that when the cholera prevailed in Oxford, 

 in 1850, sixteen cases occurred in the higher parts of the city, which 

 were to be attributed to the fact that the houses in which they occurred 

 were connected with the sewers by means of water-closets and drain- 

 age pipes. 



Harkermann states that when the cholera raged in the prisons of 



