1'16 GEOLOGICAL SUKVEY OF THE TERRITORIES. 



sorbed by the vaporization of the water must be subtracted to obtain 

 the actual available heat produced by the combustion of a unit of this 

 coal. The results are given in column 15. (Calorific power IV.) They 

 may also be obtained by subtracting from calorific power III 64.5 units 

 of heat for each per cent, of hydrogen present in the analyses over and 

 above tliat required to form water with the oxygen present. Column 

 14 gives the relation between the heat-producing power of these coals 

 as compared with that of pure carbon, (8080.) 



It shows that many of them may be considered as having three-fourths 

 of the calorific power of that substance as represented by perfectly 

 purified charcoal. These numbers, of course, can never be fully real 

 ized in actual i^ractice, but neither can the full calorific power of pure 

 carbon ; they still serve, however, for purposes of comparison, and they 

 show that the inherent or potential capabilities of these coals are far 

 greater than they are usually supposed to be. 



So much for the quantity of heat that these coals are capable of pro- 

 ducing, if completely and perfectly burned. The temperature produced 

 by this combustion, and which is the chief consideration in the applica- 

 tion of fuel to practical purposes, is another matter. This temperature 

 depends on the rapidity or intensity of the combustion in a given space, 

 and the amount and specific heats of the gases produced by it, and may 

 be as seriously affected by the physical behavior of the fuel as by its 

 chemical composition. That the latter is favorable to the production of 

 high heats is shown above ; but before being able to judge of the best 

 mode of application of these coals, their physical characters and behavior 

 must be first examined. 



PHYSICAL CHARAOTEES OE THE LIGNITIC COALS OF THE PLAINS. 



The.lignitic coals of Colorado occur varying from mere streaks of 

 carbonaceous matter to beds 16 feet in thickness. "For the most part 

 they are remarkably free from impurities, it being not rare to see a face 

 of 8 or even 10 feet of clean coal of brilliant luster, perfectly sound and 

 solid in the mine, without a particle of slate or any visible foreign mat- 

 ter that would injure it. Iron pyrites, however, may generally be de- 

 tected in small flakes and thin disks, but very rarely in sufficient quan- 

 tity to be injurious. Mineral resin is a common ingredient." * 



Their specific gravity is seldom below 1.3, sometimes 1.4. With one 

 or two exceptions, in which the color is a dull black, they all possess a 

 high shining luster, and cleave readily into cubical blocks. When well 

 protected they may remain a long time unchanged, but on exposure to 

 the atmosphere 'they disintegrate very rapidly. "This tendency to 

 crumble is the cause of great waste at the mines — all the greater that 

 these tertiary coals can scarcely ever be made to melt and agglutinate 

 into a firm coke. With rare exceptions, when submitted to the coking 

 process they retain their form or crumble into a dry powder." " The 

 coal kindles and burns freely, making a bright fire with a yellow blaze 

 and comparatively little smoke ; the odor of this is not so strong or 

 disagreeable as that of the bituminous coals, and somewhat resembles 

 the smell of burning peat. The smoke is not always dark and thick, 

 but is sometimes of a light-g-ray color. The ashes are remarkably light 

 and bulky." t 



* Hodgo on the Tertiary coals of the West, (Hayden's Report for 1870, p. 319.) 

 + Ibid., pp. 319-320. 



