COAL. 



from an old shaft of the mine, and in Figs. N and 

 of PI. XIX, obtained in the mine at tin- time of 

 examination. 



The prevalence of clay partings in the coal 

 is very noticeable, these and the bone about the 

 middle of the bed being remarkably persistent. 

 The hands <>f coal, claw and sandstone, imme- 

 diately above the scam, in fact forming a part 

 of it, arc irregular in occurrence, their lines of 

 deposition rising or sinking, the individual strata 

 thinning to a knife-edge or attaining almost the 

 maximum thickness of the series. 



The coal itself is a thoroughly representa- 

 tive type of the lignite of the plains: its streak 

 is brown; it weathers rapidly and disintegrates 

 completely: it contains 25 per cent water, yields 

 a large amount of ash, and burns with evolution 

 of comparatively little heat. 



THE COAL. 



3o' Gray Shale 

 3 Coal and Shale 



5/6 Gray 5ha/e 



rv/th 

 few Ironstones 



3o Sandstone 



76 "Coal, Several 

 clay streaks 



Fig. 1(1.— Section of coal measure! 

 of upper Laramie ;it Soranton. 



CHEMICAL ANALYSES OF INDIVIUTAL SAMPLES. 



The analyses in Table I may be regarded as representative, both of 

 the mines from which they were obtained and the areas in which the mines 

 are. With the exception of Nos. .'57, 127, 128, and 129, all are of com- 

 mercial mine samples, but owing to the ease with which the slate or other 

 partings are separated in mining, and the freedom of the coal itself from 

 impurities, the analyses are available for scientific discussion of the coals 

 as well as for their commercial comparison. The samples were taken 

 directly across the seams from fresh surfaces cut for the purpose. Rooms 

 long abandoned, and others newly opened, were sampled to show the 

 degree of deterioration on long exposure underground or to illustrate 

 possible variation in the physical and chemical conditions of the coal. 

 Such portions of the bed as were excluded in shipping — partings, pyrite 

 balls, silicified roots, and bone — were also excluded from the samples, but 



