Polytechnic Association. 945 



The substances that are driven off in the formation of coal are 

 sometimes found stored at a point more or less remote from the coal 

 from which they are derived, as in the case of the coal-oil deposits. 



To return to the lignites. I have here many typical specimens of 

 them. They contain more than ten per cent of water, and sixteen 

 per cent of oxygen. The oxygen we do not want to buy by the ton, 

 and the water is not only useless, but it must be converted into steam 

 and driven off. For these reasons the lignites are inferior in value to 

 bituminous coal. Some of them contain so much water that they 

 crack into minute fragments, and there is great loss in mining and in 

 handling them. At Santa Fe there is a lignite which is saturated with 

 water, and so soft that it can be cut with a spade, but it is of no value 

 as fuel. In Sonora there are beds of coal of the triassic age ; and 

 there are, in that vicinity, some small beds of lignite which have been 

 converted into anthracite coal. 



The lignites of the far west being of less intrinsic value as fuel than 

 coal, can only be used with economy where they are produced ; and 

 they sometimes contain, when taken from the mine, so large a pro- 

 portion of water, that they cannot well be transported. The San 

 Francisco market is supplied from various beds of lignites found in 

 that vicinity. 



Prof. N. exhibited specimens of lignites from Alaska, San Francisco, 

 Denver, Wyoming, Utah, Sonora and other points, with tables show- 

 ing their constituents, and showing upon the map the locations. 



With regard to the value of these materials as a fuel, we have beds 

 no less extensive than those of the carboniferous period. I have com- 

 puted from the best data that I could obtain that there are not less 

 than 50,000 square miles of them. They vary very much in value, from 

 the different proportions they contain of oxygen and of water. The 

 quantity of ash is not large, and they contain, on the average, about 

 as much sulphur as our bituminous coal. To determine the calorific 

 power of a fuel, we have simply to make an ultimate analysis of it ; 

 and then, supposing it to have the average physical condition, to be 

 sufficiently compact and solid to be handled, to be put into the fur- 

 nace, and allow the draft to pass through it, we can determine very 

 nearly its value. To give you the result, without detaining you too 

 long with the mode of computation, I find that the heating power of 

 these lignites is about five-eighths of that of a good quality of our 

 bituminous coal. 



It has been proved that the best coals for making steam are those 

 which have not lost all of their volatile constituents, but which have 

 [Inst.] 60 



