490 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Frequent allusions having been made to the draft of chimneys, he 

 proposed to illustrate, on the black-board, the composition of the 

 air as it entered the furnace, and the relative quantit}- of oxygen 

 and nitrogen it contained, together with the volume and composi- 

 tion of the products of combustion. The element nitrogen takes 

 no active part in the process ot combustion; it, however, becomes 

 highlj' heated, and thus rarefied and mixed with carbonic acid, 

 and sometimes carbonic ox^-d, assists in bearing rapidly away the 

 gases resulting from the process of burning. 



Several other gentlemen participated in the debate, which is to 

 be renewed at the meeting on Thursday evening, September 20, 

 and to that time the Association adjourned. 



American Institute Polytechnic Association, ) 

 September 20th, 1867. ] 



Prof. S. D. Tillman, Chairman; Mr. T. D. Stetson, Sec'y. 



The chairman read the following letter addressed to the Pre- 

 sident of the Institute : ' / 



Utilization of Gas House Lime. 



No. 8 Pine Street, Neav York, ) 

 August 21th, 18GG. \ 



Hon. Horace Greeley, President of the American Institute : 



Sir — The editors of the Mining d' Petroleum Stcmdard and 

 American Gas-Light Journal have called to my notice a report 

 of proceedings of the Farmers' Club of the Institute, wherein 

 some information was asked relative to the treatment of gas house 

 lime. As the question implies a wider scope than expressed in 

 the report, and having bestowed some attention to this speciality, 

 and with, I consider, satisfactory results, I respectfully submit 

 what follows, for whom it may concern. 



As lime is known to be the cheapest and most convenient sub- 

 stance yet discovered for purifying commercial gas, it follows that 

 the purer the limestone from which it is made, the better will be 

 the result. It is used in a wet or liquid state, as milk of lime, in 

 many cases, but in this country is usually employed as hydrated 

 or water slacked, in nearly a dry condition; shell lime is also used 

 to a cfi'eat extent in New York. 



The lime is laid about three inches deep upon wooden selves or 



