1 43 On the OPENINGS 



No. XVII. 



Defcriplion of a Stopper for the Openings by which the 

 Sewers of Cities receive the Water of their Drains, By 

 Mr. John Fraser, of Chelfea^ London, 



Read, Sept. T"^ HE parts of this ftopper refemble fo much 

 It), iSoo. X the hopper anil fhoe of a grift-mill, that 

 they may be called by thofe names. The opening by 

 which the water from the drains pafles down into the 

 common fewer, is generally fecured at its orifice by a 

 curb or frame of wood, and by an iron grating which 

 prevents large bodies from falling in. Let the iron grat- 

 ing open on a hinge, then fet into the curb a hopper of 

 wood, flieet or caft-iron, fo clofely fitted at its top to 

 the curb as to prevent the paffage of air between them. 

 Under this hopper fufpend a (hoe or box, clofe except at 

 top, within which the lower opening of the hopper may 

 empty itfelf, and the water flow off over the brim of the 

 fhoe, into the fewer. When the water ceafes to flow, 

 the flioe remaining full, keeps the lower opening of the 

 hopper clofed, fo that no air can pafs up through it. The 

 iron grating is fhut down on the hopper to keep bodies 

 from falling into it. 



In Charlefton and Savannah, where the ftreets are not 

 paved, and are very fandy, fuch quantities of fand are 

 carried by currents of air down through the drain holes 

 into the fewer, as to choke that entirely. To prevent 

 this, lay a lid on the hopper, fitted to it, and having an 

 aperture in its centre of half its own diameter. Under 

 this aperture, and very near to it, and confequently with- 

 in the hopper, fufpend a pan or other veitel fomewhat 

 larger than the aperture, but lefs than the lid itfelf. The 



fand 



