Polytechnic Association. (363 



If a communication is then made and we have a rarefaction of 

 the air in the main reservoir, it is plain that a corresponding rarefac- 

 tion will take place in the sub-reservoir. Then, after cutting off the 

 connection with the main reservoir, a cock in one of the main pipes 

 is opened, and it is evident that the atmosphere pressing upon the 

 contents of the branches of this main pipe must force these contents 

 in the direction of the reservoir. Should they not be forced entirely 

 to the reservoir, the valves in connection with each branch pipe would, 

 prevent any return, and a second exhaustion of the reservoir would 

 enable them to be driven still farther. By a proper manipulation of 

 the cocks the contents of all the pipes of a sub-complex may be con- 

 veyed in less than five minutes in the main reservoir. I am not 

 aware that Mr. Liernur has yet proposed any plan by which the fecal 

 matter should be conveyed in pipes from these main reservoirs to 

 without the city limits. But I do not apprehend that engineers 

 would find much difficulty in devising such means, provided they 

 were furnished with the necessary stimulant. The reason, perhaps, 

 is, that most of the European cities have, apparently, obtained their 

 growth, and may almost be said to be " fenced in," not being sur- 

 rounded with the subarb reservoirs for miles around, so that immedi- 

 ately outside them farming and gardening commences ; and the 

 practice, so far, has been where this sj-stem is in operation to fill the 

 stuff into barrels at a decanting station within the city, and the farm- 

 ers and gardeners carted these casks away themselves, paying at the 

 same time about twenty-five cents per hundred weight for their con- 

 tents. It does not require a very extended knowledge to understand 

 the general principle upon which this system works. But, as a matter 

 of course, when it comes to a practical application of it, there are many 

 details that time will not allow me to enter into the discussion of. 



For instance, the construction of the air-pumps is such that, with a 

 two horse-power engine, we may, in half a minute, reduce the air in 

 a reservoir, containing 100 cubic feet, to such an extent, that water 

 would be raised twenty-seven feet in a pipe communicating with it. 

 The construction of the valves on the branch pipes are also an inge- 

 nious contrivance. 



This system, if in proper working, would certainly accomplish two 

 important objects, viz. : It would prevent any possibility of the earth 

 being further impregnated with corrupt and decomposed fecal 

 matter. Secondly, it would prevent this matter from being discharged 

 into our rivers and harbors, the practice of which has alreadj' in many 



