PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 491 



trays, of convenient size for handling, which are placed in iron 

 purifying chests in layers or. stages, with intermediate spaces, 

 until the chest is filled, and which is finally shnt by a closely 

 fitting water sealed cover. The gas, admitted at the bottom of 

 the chest, is made to permeate and pass through the lime, which 

 in the transit, absorbs sulphuretted hydrogen, carbonic acid, and 

 other impurities from the gas which passes out at the top of the 

 chest. 



After the lime has done its work, or become surcharged with 

 impurities — as is generally the case — the gas is shut off from that 

 and turned on to a chest having a fresh supply of lime. The con- 

 tents of the first chest have now to be removed, which, until re- 

 cently, was accomplished in the following manner by all the gas- 

 works in this city: 



The cover of the chest being removed, the seives are one by one 

 taken out and emptied either into a barrow by which the lime is 

 trundled ofl'to a waste heap, or is thrown in a pile and afterwards 

 removed to the deposit heap, usually upon or adjacent to a wharf. 

 Now, as this surcharged lime has a great affinity for air, it absorbs 

 it rapidly as soon as exposed, and hence becomes quite hot. The 

 heat disengages the gases, which are thereby evolved into the air, 

 greatly to the inconvenience — if with no other ill effect — of all 

 persons in the neighborhood, and often those along distance away. 

 The lime thus treated becomes inodorous after a few hours, and is 

 used, in some cases, to fill in waste ground, in others is sold at 

 trifling rates for use upon land or mixed with fertilizers, with, I 

 consider, very questionable utility. 



The noxious odors from gas works, of which there has been so 

 long and such frequent complaint in this city, arise almost exclu- 

 sively from the causes here given ; all other offensive smells are 

 either insignificant, or controllable with proper care by the means 

 long used by the companies. 



The recent action of the board of health upon the "gas house 

 nuisance" has induced an improvement by the very distinguished 

 engineer of the Manhattan Gas Co., who deserves the gratitude 

 of the complainants for a clever practical device, to at least miti- 

 gate the evil under peculiar emergencies. The action of the 

 board (so properly potent) was almost mandatory; its imperative 

 commands were slightly modified upon a promise to experimenta- 

 lize. Chemistry, after various trials, failed to meet the issue with 

 present arrangements; it was impractical to undertake extensive 



