PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 569 



which produces the best gas is the bog pqat coal ; the coal now most in 

 use for making gas, is the Pennsylvania, but the English coal is preferred. 

 The other coals are in the order of their value, as follows : Pennsylvania, 

 Mount Stirling, Mount Carbon, Beaver Bay. The other coals stand : Cape 

 Breton, Cow Bay, Glase Bay, Lingum Bay, 



The Pennsylvania coal cannot be had in sufficient quantities. Eecent 

 experiments have shown that a very fine gas can be made from petroleum, 

 but in order to make this process valuable for general use, the petroleum 

 must be sold in this city at five cents a gallon before it can compete with 

 coal gas at all ; that is, if coal is sold at five dollars a ton, petroleum 

 should be at five cents a gallon. Among the improvements which the 

 manufacture of coal gas has undergone is that of using fire clay retorts, 

 instead of the iron ones formerly used, they are also much cheaper, as the 

 iron retorts would cost forty-five dollars, and wear or burn out in eight 

 months, but the clay ones cost twenty-five dollars, and will last three 

 years, and they can be cleaned much more readily. The English com- 

 panies have lately been using what are termed through-retorts, with doors 

 at both ends, but these have been tried in this country and were not suc- 

 cessful, as they had to charge both ends at the same time, and in so doing 

 pieces of carbon would very often fly out in the faces of the men at work 

 charging them. The form of the retorts has also changed. The vertical 

 sections of the first ones were cylindrical, and again oval, they are now in 

 the shape of the letter D, the round side being uppermost. The experiments 

 being made in the manufacture of coal gas, are very numerous. Some 

 companies have the best chemical talent employed in conducting experi- 

 ments ; one of these chemists is a member of this Institute. The President 

 of one of the companies in this city, told me that more improvements in 

 the manufacture of gas have been made here than in all other parts of the 

 world combined. 



Mr. Jireh Bull. — The statement of Dr. Rich, that coal at five dollars a 

 ton was cheaper than petroleum at five cfents a gallon, I should say could 

 not be true, if the quality of the gas produced was taken into consideration. 

 A small gas manufactory was established at Ballston Spa, N. Y., a few 

 years ago, in which resin was the substance distilled. When owing to the 

 war, resin could not be obtained, resort was had to petroleum, and after 

 altering the burners so as to consume only oue-half the amount of gas, the 

 light gave entire satisfaction, and the gas was supplied at the same rates 

 of prices as when resin was used. 



The Chairman remarked that the early trials of Murdock and others failed 

 because the gaseous products were not properly combined, and were unpu- 

 rified. The real intrcjduction of coal gas was when these obstacles were 

 nearly overcome. He proposed to direct attention to the process of distil- 

 lation of coal and the various products resulting therefrom. 



The materials most in use for the manufacture of illuminating gas are 

 coals having a large percentage of hydrogen, oil, resin, peat, wood, and pe- 

 troleum. Of the latter substance, but little is yet known, and it is impos- 

 sible to give a clear statement of all tite products produced by its distilla- 

 tion. Resin and oil, owing to their present high price, cannot be consi- 

 dered as economical materials. Feat and wood, containing a large per. 



